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Página 2.310 de 2.904

  • Ciências da Natureza

    Física

    O gráfico mostra como varia a intensidade da força eletrostática (F) entre duas partículas eletrizadas em função da distância (d) entre elas.

    Imagem da questão de Física, UEA 2018, Eletricidade

    Baseando-se nas informações do gráfico, pode-se afirmar que a razão F2/F1 é igual a
    Escolha uma alternativa para a questão ccd52be6-03
  • Ciências da Natureza

    Física

    A potência elétrica consumida em um dia, em função do tempo, em determinada residência, está representada de forma simplificada no gráfico:

    Imagem da questão de Física, UEA 2018, Eletricidade

    Considere que o valor cobrado por 1 kWh de energia elétrica pela concessionária local seja de R$ 0,30. De acordo com o gráfico, o valor a ser pago por um dia de consumo, na residência citada, é de
    Escolha uma alternativa para a questão ccd8410d-03
  • Linguagens

    Inglês

    How a Canadian Chain Is Reinventing Book Selling

    By Alexandra Alter

                About a decade ago, Heather Reisman, the chief executive of Canada’s largest bookstore chain, was having tea with the novelist Margaret Atwood when Ms. Atwood inadvertently gave her an idea for a new product. Ms. Atwood announced that she planned to go home, put on a pair of cozy socks and curl up with a book. Ms. Reisman thought about how appealing that sounded. Not long after, her company, Indigo, developed its own brand of plush “reading socks.” They quickly became one of Indigo’s signature gift items.

                “Last year, all my friends got reading socks,” said Arianna Huffington, the HuffPost cofounder and a friend of Ms. Reisman’s, who also gave the socks as gifts to employees at her organization Thrive. “Most people don’t have reading socks — not like Heather’s reading socks.”

                Over the last few years, Indigo has designed dozens of other products, including beach mats, scented candles, inspirational wall art, Mason jars, crystal pillars, bento lunchboxes, herb growing kits, copper cheese knife sets, stemless champagne flutes, throw pillows and scarves.

                It may seem strange for a bookstore chain to be developing and selling artisanal soup bowls and organic cotton baby onesies. But Indigo’s approach seems not only novel but crucial to its success and longevity. The superstore concept, with hulking retail spaces stocking 100,000 titles, has become increasingly hard to sustain in the era of online retail, when it’s impossible to match Amazon’s vast selection. 

                Indigo is experimenting with a new model, positioning itself as a “cultural department store” where customers who wander in to browse through books often end up lingering as they impulsively shop for cashmere slippers and crystal facial rollers, or a knife set to go with a new Paleo cookbook. Over the past few years, Ms. Reisman has reinvented Indigo as a Goop-like, curated lifestyle brand, with sections devoted to food, health and wellness, and home décor. 

             Ms. Reisman is now importing Indigo’s approach to the United States. Last year, Indigo opened its first American outpost, at a luxury mall in Millburn, N.J., and she eventually plans to open a cluster of Indigos in the Northeast. Indigo’s ascendance is all the more notable given the challenges that big bookstore chains have faced in the United States. Borders, which once had more than 650 locations, filed for bankruptcy in 2011. Barnes & Noble now operates 627 stores, down from 720 in 2010, and the company put itself up for sale last year. Lately, it has been opening smaller stores, including an 8,300-square-foot outlet in Fairfax County, Va.

                “Cross-merchandising is Retail 101, and it’s hard to do in a typical bookstore,” said Peter Hildick-Smith, president of the Codex Group, which analyzes the book industry. “Indigo found a way to create an extra aura around the bookbuying experience, by creating a physical extension of what you’re reading about.”

                The atmosphere is unabashedly intimate, cozy and feminine — an aesthetic choice that also makes commercial sense, given that women account for some 60 percent of book buyers. A section called “The Joy of the Table” stocks Indigobrand ceramics, glassware and acacia wood serving platters with the cookbooks. The home décor section has pillows and throws, woven baskets, vases and scented candles. There’s a subsection called “In Her Words,” which features idea-driven books and memoirs by women. An area labeled “A Room of Her Own” looks like a lush dressing room, with vegan leather purses, soft gray shawls, a velvet chair, scarves and journals alongside art, design and fashion books.

                Books still account for just over 50 percent of Indigo’s sales and remain the central draw; the New Jersey store stocks around 55,000 titles. But they also serve another purpose: providing a window into consumers’ interests, hobbies, desires and anxieties, which makes it easier to develop and sell related products. 

                Publishing executives, who have watched with growing alarm as Barnes & Noble has struggled, have responded enthusiastically to Ms. Reisman’s strategy. “Heather pioneered and perfected the art of integrating books and nonbook products,” Markus Dohle, the chief executive of Penguin Random House, said in an email. 

                Ms. Reisman has made herself and her own tastes and interests central to the brand. The front of the New Jersey store features a section labeled “Heather’s Picks,” with a display table covered with dozens of titles. A sign identifies her as the chain’s “founder, C.E.O., Chief Booklover and the Heather in Heather’s Picks.” She appears regularly at author signings and store events, and has interviewed prominent authors like Malcolm Gladwell, James Comey, Sally Field, Bill Clinton and Nora Ephron. 

                When Ms. Reisman opened the first Indigo store in Burlington, Ontario, in 1997, she had already run her own consulting firm and later served as president of a soft drink and beverage company, Cott. Still, bookselling is an idiosyncratic industry, and many questioned whether Indigo could compete with Canada’s biggest bookseller, Chapters. Skepticism dissolved a few years later when Indigo merged with Chapters, inheriting its fleet of national stores. The company now has more than 200 outlets across Canada, including 89 “superstores.” Indigo opened its first revamped concept store in 2016. 

                The new approach has proved lucrative: In its 2017 fiscal year, the company’s revenue exceeded $1 billion Canadian for the first time. In its 2018 fiscal year, Indigo reported a revenue increase of nearly $60 million Canadian over the previous year, making it the most profitable year in the chain’s history. 

                The company’s dominance in Canada doesn’t guarantee it will thrive in the United States, where it has to compete not only with Amazon and Barnes & Noble, but with a resurgent wave of independent booksellers. After years of decline, independent stores have rebounded, with some 2,470 locations, up from 1,651 a decade ago, according to the American Booksellers Association. And Amazon has expanded into the physical retail market, with around 20 bookstores across the United States.

                Ms. Reisman acknowledges that the company faces challenges as it expands southward. Still, she’s optimistic, and is already scouting locations for a second store near New York.

    https://www.nytimes.com/2019/05/01

    “In Her Words” is a subsection at Indigo in which one can find
    Escolha uma alternativa para a questão ccd9bd89-9c
  • Ciências da Natureza

    Biologia

    Em 2006, foi realizada uma conferência das Nações Unidas em que se discutiu o problema do lixo eletrônico, também denominado e-waste. Nessa ocasião, destacou-se a necessidade de os países em desenvolvimento serem protegidos das doações nem sempre bem-intencionadas dos países mais ricos. Uma vez descartados ou doados, equipamentos eletrônicos chegam a países em desenvolvimento com o rótulo de “mercadorias recondicionadas”, mas acabam deteriorando- se em lixões, liberando chumbo, cádmio, mercúrio e outros materiais tóxicos.

    Imagem da questão de Biologia, ENEM 2008, Ecologia e ciências ambientais

    A discussão dos problemas associados ao e-waste leva à conclusão de que
    Escolha uma alternativa para a questão ccdafba8-bb
  • Ciências da Natureza

    Física

    O diagrama a seguir da pressão (P) em função do volume (V) mostra as transformações termodinâmicas sofridas por um gás ideal em um ciclo termodinâmico fechado.

    Imagem da questão de Física, UNIFAL-MG 2008, 1ª Lei da Termodinâmica Analise as assertivas e assinale a alternativa correta.

    I. O gás sofre uma transformação isocórica para ir de A até B.

    II. A variação da energia interna do gás só depende da variação da temperatura.

    III. O trabalho realizado pelo gás é obtido calculando a área do retângulo ABCD.

    IV. A energia interna do gás não varia quando o gás passa do estado A para o estado D. V. A temperatura em TD é igual a (P1/P2)TA.

    Escolha uma alternativa para a questão ccdb49f7-2d
  • Linguagens

    Espanhol

                           Yoani Sánchez:
           “Los cubanos están escapando a Yucatán”

    14.03.2013

           La periodista cubana Yoani Sánchez ha visitado México dentro de la gira por América y Europa que empezó el 17 de febrero tras concederle el Gobierno de La Habana un pasaporte que le había denegado veinte veces durante los últimos cinco años, según su recuento. El periplo de la autora del blog Generación Y, un cuaderno de bitácora crítico con la realidad cotidiana de su país por el que ha recibido premios internacionales, ha estado marcado por la muerte del presidente venezolano Hugo Chávez, cuya generosidad petrolera era esencial para la maltrecha economía de la isla.
            La desaparición del líder bolivariano crea incertidumbre en Cuba. Yoani Sánchez, que vivió de joven la dramática crisis de recursos provocada en su país por la caída de la Unión Soviética dice que para los cubanos el final de Chávez tiene dos lecturas: “La mayoría asocia su pérdida con el posible regreso de los cortes eléctricos, con la caída de la economía, pero por otro lado también piensa que sin él se pierde el subsidio y tal vez Raúl Castro se vea obligado a acelerar las reformas”.
            En un eventual escenario de transición democrática en Cuba, un país que por tradición histórica y proximidad geográfica podría tener un papel significativo en el reordenamiento del panorama poscastrista es México. La periodista advierte de que este país ya es una referencia básica en la vida de la isla. “Hay muchos cubanos escapando a través del mar para llegar a México; no solamente escapan hacia Florida, también escapan hacia Yucatán [Estado situado en el sureste de México, a unos 200 kilómetros de la costa cubana]”. Una circunstancia que empieza a preocupar al Gobierno mexicano.
            Yoani dio una charla abierta a preguntas en el Senado mexicano. Allí, dos mujeres del público la increparon y mostraron símbolos en contra de ella. “Una llevaba una bandera estadounidense con mi rostro pegado y la otra llevaba billetes de cien dólares con mi rostro pegado. Era una especie de iconografía a medio camino entre Estados Unidos y yo”. Antes del incidente otra persona le había preguntado si Cuba está en un momento de transición. “Respondí que yo creo que sí, pero no por la voluntad gubernamental, sino porque hay algo en transición en el interior de los cubanos, un deseo de cambio, de transformación, de hasta aquí hemos llegado”.
           En mayo la cubana espera estar de vuelta en su casa de La Habana, un piso en la decimocuarta planta de un edificio diseñado con criterios arquitectónicos de la antigua Yugoslavia comunista.


                                               (www.elpais.com. Adaptado.)

    De acuerdo con el cuarto párrafo del texto, Yoani cree que Cuba está en un momento de transición
    Escolha uma alternativa para a questão ccdb6f33-02
  • Ciências da Natureza

    Química

    Dissolução fracionada é uma técnica utilizada para realizar a separação dos componentes de uma mistura entre
    Escolha uma alternativa para a questão ccdbbf84-03
  • Linguagens

    Inglês

    How a Canadian Chain Is Reinventing Book Selling

    By Alexandra Alter

                About a decade ago, Heather Reisman, the chief executive of Canada’s largest bookstore chain, was having tea with the novelist Margaret Atwood when Ms. Atwood inadvertently gave her an idea for a new product. Ms. Atwood announced that she planned to go home, put on a pair of cozy socks and curl up with a book. Ms. Reisman thought about how appealing that sounded. Not long after, her company, Indigo, developed its own brand of plush “reading socks.” They quickly became one of Indigo’s signature gift items.

                “Last year, all my friends got reading socks,” said Arianna Huffington, the HuffPost cofounder and a friend of Ms. Reisman’s, who also gave the socks as gifts to employees at her organization Thrive. “Most people don’t have reading socks — not like Heather’s reading socks.”

                Over the last few years, Indigo has designed dozens of other products, including beach mats, scented candles, inspirational wall art, Mason jars, crystal pillars, bento lunchboxes, herb growing kits, copper cheese knife sets, stemless champagne flutes, throw pillows and scarves.

                It may seem strange for a bookstore chain to be developing and selling artisanal soup bowls and organic cotton baby onesies. But Indigo’s approach seems not only novel but crucial to its success and longevity. The superstore concept, with hulking retail spaces stocking 100,000 titles, has become increasingly hard to sustain in the era of online retail, when it’s impossible to match Amazon’s vast selection. 

                Indigo is experimenting with a new model, positioning itself as a “cultural department store” where customers who wander in to browse through books often end up lingering as they impulsively shop for cashmere slippers and crystal facial rollers, or a knife set to go with a new Paleo cookbook. Over the past few years, Ms. Reisman has reinvented Indigo as a Goop-like, curated lifestyle brand, with sections devoted to food, health and wellness, and home décor. 

             Ms. Reisman is now importing Indigo’s approach to the United States. Last year, Indigo opened its first American outpost, at a luxury mall in Millburn, N.J., and she eventually plans to open a cluster of Indigos in the Northeast. Indigo’s ascendance is all the more notable given the challenges that big bookstore chains have faced in the United States. Borders, which once had more than 650 locations, filed for bankruptcy in 2011. Barnes & Noble now operates 627 stores, down from 720 in 2010, and the company put itself up for sale last year. Lately, it has been opening smaller stores, including an 8,300-square-foot outlet in Fairfax County, Va.

                “Cross-merchandising is Retail 101, and it’s hard to do in a typical bookstore,” said Peter Hildick-Smith, president of the Codex Group, which analyzes the book industry. “Indigo found a way to create an extra aura around the bookbuying experience, by creating a physical extension of what you’re reading about.”

                The atmosphere is unabashedly intimate, cozy and feminine — an aesthetic choice that also makes commercial sense, given that women account for some 60 percent of book buyers. A section called “The Joy of the Table” stocks Indigobrand ceramics, glassware and acacia wood serving platters with the cookbooks. The home décor section has pillows and throws, woven baskets, vases and scented candles. There’s a subsection called “In Her Words,” which features idea-driven books and memoirs by women. An area labeled “A Room of Her Own” looks like a lush dressing room, with vegan leather purses, soft gray shawls, a velvet chair, scarves and journals alongside art, design and fashion books.

                Books still account for just over 50 percent of Indigo’s sales and remain the central draw; the New Jersey store stocks around 55,000 titles. But they also serve another purpose: providing a window into consumers’ interests, hobbies, desires and anxieties, which makes it easier to develop and sell related products. 

                Publishing executives, who have watched with growing alarm as Barnes & Noble has struggled, have responded enthusiastically to Ms. Reisman’s strategy. “Heather pioneered and perfected the art of integrating books and nonbook products,” Markus Dohle, the chief executive of Penguin Random House, said in an email. 

                Ms. Reisman has made herself and her own tastes and interests central to the brand. The front of the New Jersey store features a section labeled “Heather’s Picks,” with a display table covered with dozens of titles. A sign identifies her as the chain’s “founder, C.E.O., Chief Booklover and the Heather in Heather’s Picks.” She appears regularly at author signings and store events, and has interviewed prominent authors like Malcolm Gladwell, James Comey, Sally Field, Bill Clinton and Nora Ephron. 

                When Ms. Reisman opened the first Indigo store in Burlington, Ontario, in 1997, she had already run her own consulting firm and later served as president of a soft drink and beverage company, Cott. Still, bookselling is an idiosyncratic industry, and many questioned whether Indigo could compete with Canada’s biggest bookseller, Chapters. Skepticism dissolved a few years later when Indigo merged with Chapters, inheriting its fleet of national stores. The company now has more than 200 outlets across Canada, including 89 “superstores.” Indigo opened its first revamped concept store in 2016. 

                The new approach has proved lucrative: In its 2017 fiscal year, the company’s revenue exceeded $1 billion Canadian for the first time. In its 2018 fiscal year, Indigo reported a revenue increase of nearly $60 million Canadian over the previous year, making it the most profitable year in the chain’s history. 

                The company’s dominance in Canada doesn’t guarantee it will thrive in the United States, where it has to compete not only with Amazon and Barnes & Noble, but with a resurgent wave of independent booksellers. After years of decline, independent stores have rebounded, with some 2,470 locations, up from 1,651 a decade ago, according to the American Booksellers Association. And Amazon has expanded into the physical retail market, with around 20 bookstores across the United States.

                Ms. Reisman acknowledges that the company faces challenges as it expands southward. Still, she’s optimistic, and is already scouting locations for a second store near New York.

    https://www.nytimes.com/2019/05/01

    According to the text, the response of publishing executives to Ms. Reisman’s strategy of “integrating book and non-book products” has been
    Escolha uma alternativa para a questão ccdda2e2-9c
  • Ciências da Natureza

    Química

    Um íon de carga 2+ apresenta o mesmo número de elétrons que o gás nobre argônio, e seu núcleo contém 20 nêutrons. O número atômico e o número de massa desse íon são, respectivamente,
    Escolha uma alternativa para a questão ccdedb74-03
  • Ciências da Natureza

    Química

    Elementos metálicos tendem a reagir doando seus elétrons, sendo que essa tendência aumenta com o aumento do raio atômico. A sequência que apresenta elementos metálicos em ordem crescente de reatividade é
    Escolha uma alternativa para a questão cce1e55c-03
  • Linguagens

    Inglês

    How a Canadian Chain Is Reinventing Book Selling

    By Alexandra Alter

                About a decade ago, Heather Reisman, the chief executive of Canada’s largest bookstore chain, was having tea with the novelist Margaret Atwood when Ms. Atwood inadvertently gave her an idea for a new product. Ms. Atwood announced that she planned to go home, put on a pair of cozy socks and curl up with a book. Ms. Reisman thought about how appealing that sounded. Not long after, her company, Indigo, developed its own brand of plush “reading socks.” They quickly became one of Indigo’s signature gift items.

                “Last year, all my friends got reading socks,” said Arianna Huffington, the HuffPost cofounder and a friend of Ms. Reisman’s, who also gave the socks as gifts to employees at her organization Thrive. “Most people don’t have reading socks — not like Heather’s reading socks.”

                Over the last few years, Indigo has designed dozens of other products, including beach mats, scented candles, inspirational wall art, Mason jars, crystal pillars, bento lunchboxes, herb growing kits, copper cheese knife sets, stemless champagne flutes, throw pillows and scarves.

                It may seem strange for a bookstore chain to be developing and selling artisanal soup bowls and organic cotton baby onesies. But Indigo’s approach seems not only novel but crucial to its success and longevity. The superstore concept, with hulking retail spaces stocking 100,000 titles, has become increasingly hard to sustain in the era of online retail, when it’s impossible to match Amazon’s vast selection. 

                Indigo is experimenting with a new model, positioning itself as a “cultural department store” where customers who wander in to browse through books often end up lingering as they impulsively shop for cashmere slippers and crystal facial rollers, or a knife set to go with a new Paleo cookbook. Over the past few years, Ms. Reisman has reinvented Indigo as a Goop-like, curated lifestyle brand, with sections devoted to food, health and wellness, and home décor. 

             Ms. Reisman is now importing Indigo’s approach to the United States. Last year, Indigo opened its first American outpost, at a luxury mall in Millburn, N.J., and she eventually plans to open a cluster of Indigos in the Northeast. Indigo’s ascendance is all the more notable given the challenges that big bookstore chains have faced in the United States. Borders, which once had more than 650 locations, filed for bankruptcy in 2011. Barnes & Noble now operates 627 stores, down from 720 in 2010, and the company put itself up for sale last year. Lately, it has been opening smaller stores, including an 8,300-square-foot outlet in Fairfax County, Va.

                “Cross-merchandising is Retail 101, and it’s hard to do in a typical bookstore,” said Peter Hildick-Smith, president of the Codex Group, which analyzes the book industry. “Indigo found a way to create an extra aura around the bookbuying experience, by creating a physical extension of what you’re reading about.”

                The atmosphere is unabashedly intimate, cozy and feminine — an aesthetic choice that also makes commercial sense, given that women account for some 60 percent of book buyers. A section called “The Joy of the Table” stocks Indigobrand ceramics, glassware and acacia wood serving platters with the cookbooks. The home décor section has pillows and throws, woven baskets, vases and scented candles. There’s a subsection called “In Her Words,” which features idea-driven books and memoirs by women. An area labeled “A Room of Her Own” looks like a lush dressing room, with vegan leather purses, soft gray shawls, a velvet chair, scarves and journals alongside art, design and fashion books.

                Books still account for just over 50 percent of Indigo’s sales and remain the central draw; the New Jersey store stocks around 55,000 titles. But they also serve another purpose: providing a window into consumers’ interests, hobbies, desires and anxieties, which makes it easier to develop and sell related products. 

                Publishing executives, who have watched with growing alarm as Barnes & Noble has struggled, have responded enthusiastically to Ms. Reisman’s strategy. “Heather pioneered and perfected the art of integrating books and nonbook products,” Markus Dohle, the chief executive of Penguin Random House, said in an email. 

                Ms. Reisman has made herself and her own tastes and interests central to the brand. The front of the New Jersey store features a section labeled “Heather’s Picks,” with a display table covered with dozens of titles. A sign identifies her as the chain’s “founder, C.E.O., Chief Booklover and the Heather in Heather’s Picks.” She appears regularly at author signings and store events, and has interviewed prominent authors like Malcolm Gladwell, James Comey, Sally Field, Bill Clinton and Nora Ephron. 

                When Ms. Reisman opened the first Indigo store in Burlington, Ontario, in 1997, she had already run her own consulting firm and later served as president of a soft drink and beverage company, Cott. Still, bookselling is an idiosyncratic industry, and many questioned whether Indigo could compete with Canada’s biggest bookseller, Chapters. Skepticism dissolved a few years later when Indigo merged with Chapters, inheriting its fleet of national stores. The company now has more than 200 outlets across Canada, including 89 “superstores.” Indigo opened its first revamped concept store in 2016. 

                The new approach has proved lucrative: In its 2017 fiscal year, the company’s revenue exceeded $1 billion Canadian for the first time. In its 2018 fiscal year, Indigo reported a revenue increase of nearly $60 million Canadian over the previous year, making it the most profitable year in the chain’s history. 

                The company’s dominance in Canada doesn’t guarantee it will thrive in the United States, where it has to compete not only with Amazon and Barnes & Noble, but with a resurgent wave of independent booksellers. After years of decline, independent stores have rebounded, with some 2,470 locations, up from 1,651 a decade ago, according to the American Booksellers Association. And Amazon has expanded into the physical retail market, with around 20 bookstores across the United States.

                Ms. Reisman acknowledges that the company faces challenges as it expands southward. Still, she’s optimistic, and is already scouting locations for a second store near New York.

    https://www.nytimes.com/2019/05/01

    As to revenue, the figures show this model of bookstore has been an approach that is
    Escolha uma alternativa para a questão cce2e636-9c
  • Ciências da Natureza

    Química

    Leia a tirinha.

    Imagem da questão de Química, UEA 2018, Soluções e Substâncias Inorgânicas
    (https://planetatirinha.wordpress.com)

    Considerando que a concentração expressa na tirinha seja uma relação em volume e que a densidade do álcool seja igual a 0,8 g/mL, uma dose de 100 mL de rum deverá conter uma quantidade de álcool igual a
    Escolha uma alternativa para a questão cce4e33b-03
  • Ciências da Natureza

    Química

    Leia o texto para responder à questão.

    Na busca por fontes de energia limpa e renovável, a pesquisa relacionada a biocombustíveis tem trazido importantes avanços. Um exemplo disso é a utilização de matérias- -primas à base de celulose ao invés de sacarose para a produção de etanol, produzindo os chamados biocombustíveis de segunda geração. 


    Imagem da questão de Química, UEA 2018, Energias Químicas no Cotidiano
    (sites.google.com)

    O etanol é considerado uma fonte de energia limpa porque não libera gases poluentes em sua combustão, e é considerado renovável porque o gás carbônico produzido nessa reação é absorvido por vegetais que voltarão a produzir celulose em um ciclo fechado, garantindo que as gerações futuras possam usufruir dos mesmos recursos disponíveis atualmente.

    A combustão do etanol pode ser representada pela equação:

    C2H6 O (ℓ) + 3O2 (g) 2CO2 (g) + 3H2 O (ℓ)
    ∆H = –330 kJ/mol de C2H6O (ℓ)
    A matéria-prima para o biocombustível de segunda geração pertence ao grupo de biomoléculas conhecido como
    Escolha uma alternativa para a questão cce7eaa2-03
  • Ciências da Natureza

    Química

    Leia o texto para responder à questão.

    Na busca por fontes de energia limpa e renovável, a pesquisa relacionada a biocombustíveis tem trazido importantes avanços. Um exemplo disso é a utilização de matérias- -primas à base de celulose ao invés de sacarose para a produção de etanol, produzindo os chamados biocombustíveis de segunda geração. 


    Imagem da questão de Química, UEA 2018, Energias Químicas no Cotidiano
    (sites.google.com)

    O etanol é considerado uma fonte de energia limpa porque não libera gases poluentes em sua combustão, e é considerado renovável porque o gás carbônico produzido nessa reação é absorvido por vegetais que voltarão a produzir celulose em um ciclo fechado, garantindo que as gerações futuras possam usufruir dos mesmos recursos disponíveis atualmente.

    A combustão do etanol pode ser representada pela equação:

    C2H6 O (ℓ) + 3O2 (g) 2CO2 (g) + 3H2 O (ℓ)
    ∆H = –330 kJ/mol de C2H6O (ℓ)
    Na combustão de etanol, a produção de 1 mol de CO2
    Escolha uma alternativa para a questão cceaf0e9-03
  • Ciências da Natureza

    Química

    Leia o texto para responder à questão.

    Na busca por fontes de energia limpa e renovável, a pesquisa relacionada a biocombustíveis tem trazido importantes avanços. Um exemplo disso é a utilização de matérias- -primas à base de celulose ao invés de sacarose para a produção de etanol, produzindo os chamados biocombustíveis de segunda geração. 


    Imagem da questão de Química, UEA 2018, Energias Químicas no Cotidiano
    (sites.google.com)

    O etanol é considerado uma fonte de energia limpa porque não libera gases poluentes em sua combustão, e é considerado renovável porque o gás carbônico produzido nessa reação é absorvido por vegetais que voltarão a produzir celulose em um ciclo fechado, garantindo que as gerações futuras possam usufruir dos mesmos recursos disponíveis atualmente.

    A combustão do etanol pode ser representada pela equação:

    C2H6 O (ℓ) + 3O2 (g) 2CO2 (g) + 3H2 O (ℓ)
    ∆H = –330 kJ/mol de C2H6O (ℓ)
    A combinação dos óxidos formados na produção de biocombustíveis de segunda geração produz um ácido de fórmula
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  • Ciências da Natureza

    Química

          A produção de aço envolve o aquecimento do minério de ferro, junto com carvão (carbono) e ar atmosférica em uma série de reações de oxirredução. O produto é chamado de ferro-gusa e contém cerca de 3,3% de carbono. Uma forma de eliminar o excesso de carbono é a oxidação a partir do aquecimento do ferro-gusa com gás oxigênio puro. Os dois principais produtos formados são aço doce (liga de ferro com teor de 0,3% de carbono restante) e gás carbônico. As massas molares aproximadas dos elementos carbono e oxigênio são, respectivamente, 12 g/mol e 16 g/mol.

    LEE. J. D Química Inorgânica não tão concisa. São Paulo: Edgard Blucher. 1999 (adaptado).

    Considerando que um forno foi alimentado com 2,5 toneladas de ferro-gusa, a massa de gás carbônico formada, em quilogramas, na produção de aço doce, é mais próxima de

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    Química

    Leia o texto para responder à questão.

    O processo de conversão do nitrogênio atmosférico (N2) em moléculas que as plantas possam utilizar, como por exemplo a amônia (NH3), é feito por bactérias que produzem uma enzima chamada nitrogenase, que __1__ a energia de ativação da conversão de N2 em NH3, tornando a reação mais rápida. A nitrogenase, assim como outras enzimas, são chamadas de __2__.
    As lacunas 1 e 2 são preenchidas por
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  • Ciências da Natureza

    Química

    Leia o texto para responder à questão.

    O processo de conversão do nitrogênio atmosférico (N2) em moléculas que as plantas possam utilizar, como por exemplo a amônia (NH3), é feito por bactérias que produzem uma enzima chamada nitrogenase, que __1__ a energia de ativação da conversão de N2 em NH3, tornando a reação mais rápida. A nitrogenase, assim como outras enzimas, são chamadas de __2__.
    A geometria molecular e a polaridade da molécula de amônia são:
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    Uma amostra de água mineral coletada em determinada fonte apresenta pH igual a 9,5. Isso significa que a concentração de íons H+ dessa água possui valor entre
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    Química

    A redução de 1,8 g de um metal X a partir de seu cátion trivalente consumiu 0,2 Faraday. A massa molar desse metal é igual a
    Escolha uma alternativa para a questão ccff2b6b-03