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Cincias Fsico-qumicas Reaces cido-base 8. ano
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1. Uma soluo de nitrato de amnio ficou vermelha quando se lhe
adicionarem algumas gotas de
tintura azul de tornesol. Refere se a soluo de nitrato de amnio
cida, bsica ou neutra.
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2. O bicarbonato de sdio utilizado para combater o excesso de
acidez no estmago.
Adicionamos umas gotas de soluo alcolica de fenolftalena ao
bicarbonato de sdio.
2.1. Indica qual a cor adquirida pelo indicador.
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2.2. Refere qual um valor possvel para o pH da soluo de
bicarbonato de sdio. Justifica.
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3. Observa os valores de pH abaixo indicados.
pH = 1 pH = 3 pH = 7
pH = 10 pH = 12 pH = 14
3.1. Indica quais dos valores se referem a solues cidas.
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3.2. Indica quais dos valores se referem a solues bsicas.
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3.3. Indica quais dos valores se referem a solues neutras.
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4. Uma soluo tem pH = 2. Explica como que procederias para
aumentar o pH desta soluo.
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5. As picadas das abelhas introduzem na pele um lquido cido.
Para aliviar a dor utiliza-se
carbonato de zinco.
5.1. Indica qual o carcter qumico da soluo de carbonato de zinco
(cido, bsico ou
neutro).
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5.2. Indica a escolha que fizeste na questo anterior.
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6. As picadas das vespas introduzem na pele substncias bsicas e
so tratadas com vinagre.
6.1. Explica porque que a picada das vespas no pode ser tratada
com a soluo de carbonato
de zinco.
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6.2. Refere porque que foi escolhido o vinagre.
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7. Supe que pretendias cultivar feijo num solo com pH = 5.
Refere como deverias proceder para obter um solo prprio para
esta cultura.
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Bom trabalho!
