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CHEMISTRY [2 Mark Question Answer]

Water · ICSE STD 8 (ICSE - English Medium). 9 questions.

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[2 Mark Question Answer]

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9 questions · timed · auto-graded

Question 12 Marks
What is the effect on boiling point of water when impurity is added.
Answer
Any impurity present in water lowers its freezing point and raises its boiling point.
For example, salt is added to ice to lower its melting point. Such a mixture is called a freezing-mixture. The melting is called a freezing mixture is about $-15^\circ C.$
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Question 22 Marks
Give balanced chemical equation for the reaction of water with Sodium .
Answer
$\begin{gathered}\text { sodium }+\underset{\text { (cold) }}{\text { Water }} \xrightarrow{\text { heat }} \text { sodium hydroide }+ \text { Hydrogen } \\ 2 \mathrm{Na}+2 \mathrm{H}_2 \mathrm{O} \longrightarrow 2 \mathrm{NaOH}+\underset{\text { (cold) }}{\mathrm{H}_2(\mathrm{~g})}\end{gathered}$
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Question 32 Marks
Give reason On opening a bottle of a cold drink, a fizz sound is heard.
Answer
The cold drink bottles contain carbon dioxide and are bottled under high pressure i.e. they contain a large amount of gas dissolved in them and on opening a bottle we hear a fizz sound, this is because of the solubility of $\ce{CO_2}$ gas in it and pressure in it.
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Question 42 Marks
Give reason for Table salt becomes moist during rainy season.
Answer
On exposure to air, table salt $\ce{(NaCl)}$ turns moist and ultimately forms a solution especially during rainy season because it contains impurities like magnesium chloride and calcium chloride which are deliquescent. Sodium chloride is not deliquescent.
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Question 52 Marks
Give reason for Silica gel pouches are kept in unused water bottle.
Answer
Silica get pouches are very commonly used to absorb moisture and to keep things dry. They are often kept in unused water bottles, with camera lenses etc. to keep them dry. These pouches are ideal to reuse throughout, in places at home where there is excess of moisture.
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Question 62 Marks
What do you observe when Blue vitriol is heated?
Answer
Blue vitriol is blue in colour as it contains $5$ molecules of water of crystallization $\ce{(CuSO_4.H_2O)}.$ When it is heated, it loses water of crystallization and becomes anhydrous $\ce{CuSO_4}$ which is grey-white in colour.
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Question 72 Marks
How do the solubility of a solid and a gas affected by Increase in temperature.
Answer
Solubility of a solid solute generally increases with an increase in temperature. This makes it possible to prepare supersaturated solutions.
Solubility of a gas decreases with an increase in temperature.
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Question 82 Marks
Explain the term of Solute.
Answer
A substance which dissolves in a other substances to form a solution is called solute. Solute is smaller quantity in solution.
Or
“Substance which is dissolved in solvent.” is called Solute. Solute is smaller quantity in solution.
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Question 92 Marks
Define the Soft water.
Answer
The water present in different natural sources has different substances dissolved in it. The water drawn from certain sources forms a lather with soap rather easily. Such water is called soft water.
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[2 Mark Question Answer] - CHEMISTRY STD 8 Questions - Vidyadip