1.
Write word equations and then balanced equations for the reaction taking place when −
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron filings.
2.
Plaster of Paris should be stored in a moisture-proof container. Explain why?
3.
Some fruits like mango, lemon, raw grapes, orange, etc., have a sour taste due to the presence of:
Correct Answer
B. Citric
Explanation
Citric acid is responsible for the sour taste in fruits like mango, lemon, raw grapes, and orange. It is a natural acid found in these fruits and contributes to their tart flavor. Citric acid is commonly used as a flavor enhancer and preservative in various food and beverage products due to its acidic and refreshing taste.
4.
Zinc granules on treating with an acid X, form the zinc sulphate (ZnSO4) salt along with the evolution of a gas Y which burns with a pop sound when brought near to a burning candle. Identify the acid X and gas evolved Y.
Correct Answer
C. X- SulpHuric acid and Y- Hydrogen gas
Explanation
Zinc granules react with sulphuric acid to form zinc sulphate (ZnSO4) and hydrogen gas (Y). The evolution of hydrogen gas can be identified by its ability to burn with a pop sound when brought near to a burning candle. Therefore, the acid X in this reaction is sulphuric acid and the gas evolved Y is hydrogen gas.
5.
Which of the following phenomena occur, when a small amount of acid is added to water?
i. Ionisation
ii. Neutralisation
iii. Dilution
iv. Salt formation
Correct Answer
B. 1 and 3
Explanation
When a small amount of acid is added to water, two phenomena occur: ionisation and dilution. Ionisation refers to the process in which the acid molecules break apart into ions when dissolved in water. Dilution, on the other hand, refers to the process of reducing the concentration of the acid by adding more water. Therefore, the correct answer is 1 and 3.
6.
Dilute acid does not produce carbon dioxide on being treated with:
Correct Answer
B. Lime
Explanation
When dilute acid reacts with marble, baking soda, or limestone, it produces carbon dioxide gas. However, when dilute acid reacts with lime, it does not produce carbon dioxide gas. Lime is calcium oxide (CaO), and when it reacts with acid, it forms calcium salt and water, without the release of carbon dioxide.
7.
. In the following reaction, identify the salt formed
NH4OH (aq) + H2SO4 (aq) → _____ + 2H2O (l)
Correct Answer
B. (NH4)2SO4
Explanation
When NH4OH (ammonium hydroxide) reacts with H2SO4 (sulfuric acid), they undergo a neutralization reaction. The ammonium ion (NH4+) from NH4OH combines with the sulfate ion (SO4^2-) from H2SO4 to form the salt (NH4)2SO4, which is ammonium sulfate. This reaction also produces 2 molecules of water (H2O) as a byproduct. Therefore, the correct answer is (NH4)2SO4.
8.
Copper sulphate crystals when heated strongly, lose their water of crystallization to give anhydrous copper sulphate accompanied by a change in color from:
Correct Answer
B. Blue to white
Explanation
When copper sulphate crystals are heated strongly, the water molecules that are part of the crystal structure are driven off, resulting in the formation of anhydrous copper sulphate. The blue color of the crystals is due to the presence of water molecules, and when these molecules are removed, the crystal changes to a white color.
9.
Which one of the following salts will dissolve in water to form an alkaline solution?
Correct Answer
A. Potassium carbonate
Explanation
Potassium carbonate will dissolve in water to form an alkaline solution because it is a salt that contains the carbonate ion (CO3^2-). When it is dissolved in water, the carbonate ion reacts with water to form hydroxide ions (OH^-), which are responsible for the alkaline nature of the solution. Therefore, when potassium carbonate is dissolved in water, it will increase the concentration of hydroxide ions and result in an alkaline solution.
10.
An ant’s sting can be treated with methanoic acid which will neutralise the effect of the chemical injected by the ant’s sting into our skin.
Correct Answer
B. False
Explanation
Methanoic acid, also known as formic acid, is not an effective treatment for an ant's sting. The chemical injected by an ant's sting is formic acid itself, so applying more formic acid to the sting area would not neutralize the effect. Instead, other remedies such as washing the area with soap and water, applying a cold compress, or using over-the-counter antihistamines or pain relievers may be more effective in reducing the discomfort and swelling caused by an ant's sting.
11.
Bleaching powder is used as a disinfectant for water to make germ free
Correct Answer
A. True
Explanation
Bleaching powder is commonly used as a disinfectant for water because it contains chlorine, which has strong antimicrobial properties. When added to water, bleaching powder releases chlorine gas, which effectively kills bacteria, viruses, and other harmful microorganisms present in the water. This process helps to make the water germ-free and safe for consumption. Therefore, the statement "Bleaching powder is used as a disinfectant for water to make germ-free" is true.
12.
Ammonium chloride salt will give acidic solution when dissolved in water.
Correct Answer
A. True
Explanation
When ammonium chloride is dissolved in water, it undergoes hydrolysis, which means it reacts with water to produce acidic species. Ammonium ions (NH4+) are formed, and they can donate a proton (H+) to the water molecules, resulting in an increase in the concentration of H+ ions. This increase in H+ ions makes the solution acidic. Therefore, ammonium chloride salt will indeed give an acidic solution when dissolved in water.