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To protect tooth decay we are advised to brush our teeth regularly. The nature of the toothpaste commonly used is (a) acidic (b) neutral (c) basic (d) corrosive

Answer: (c) basic The nature of toothpaste is alkaline which is basic. They neutralize the acid produced by bacteria in mouth. Usually tooth... View Article

One of the constituents of baking powder is sodium hydrogen carbonate, the other constituent is (a) hydrochloric acid (b) tartaric acid (c) acetic acid (d) sulphuric acid

Answer: (b) tartaric acid Baking powder is a mixture of sodium hydrogen carbonate and edible acid-like tartaric acid. It is a raising agent that... View Article

Common salt besides being used in the kitchen can also be used as the raw material for making: (i) washing soda (ii) bleaching powder (iii) baking soda (iv) slaked lime (a) (i) and (ii) (b) (i), (ii) and (iv) (c) (i) and (iii) (d) (i), (iii) and (iv)

Answer: (a) (i) and (ii) The chemical formula of common salt is NaCl and the chemical name of common salt is Sodium chloride. Sodium hydroxide,... View Article

Sodium hydrogen carbonate, when added to acetic acid, evolves a gas. Which of the following statements are true about the gas evolved? (i) It turns lime water milky (ii) It extinguishes a burning splinter (iii) It dissolves in a solution of sodium hydroxide (iv) It has a pungent odour (a) (i) and (ii) (b) (i), (ii) and (iii) (c) (ii), (iii) and (iv) (d) (i) and (iv)

Answer: (a) (i) and (ii) Reaction between Sodium hydrogen carbonate and acetic acid leads to the evolution of carbon-dioxide gas. CO2 turns the... View Article

If a few drops of a concentrated acid accidentally spills over the hand of a student, what should be done? (a) Wash the hand with saline solution (b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate (c) After washing with plenty of water apply a solution of sodium hydroxide on the hand (d) Neutralise the acid with a strong alkali

Answer: (b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate strong Washing affected hand with... View Article

Which of the following gives the correct increasing order of acidic strength (1) Water < Acetic acid < Hydrochloric acid (2) Water < Hydrochloric acid< Acetic acid (3) Acetic acid< Water < Hydrochloric acid (4) Hydrochloric acid< Water

Answer: (1) Water < Acetic acid < Hydrochloric acid Water is neutral in its pure form, Acetic acid is an organic acid which is weak in... View Article

A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of this pH paper to greenish-blue? (a) Lemon juice (b) Vinegar (c) Common salt (d) An antacid

Answer:(d) An antacid Sample solution turn pH paper yellowish-orange which confirms the acidic nature of the sample. To make the colour to... View Article

Sodium carbonate is a basic salt because it is a salt of (a) strong acid and strong base (b) weak acid and weak base (c) strong acid and weak base (d) weak acid and strong base

Answer: (d) weak acid and strong base Salt is formed by weak acid and a strong base. Here, Sodium is a strong base and carbonate is a weak acid.... View Article

Which of the following salts does not contain water of crystallisation? (a) Blue vitriol (b) Baking soda (c) Washing soda (d) Gypsum

Answer: (b) Baking soda Baking sodas is white amorphous powder whereas other salts given in the question are crystalline in nature. Baking... View Article

During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to (a) absorb the evolved gas (b) moisten the gas (c) absorb moisture from the gas (d) absorb Cl– ions from the evolved gas

Answer: (c) absorb moisture from the gas Calcium is a good dehydrating agent. It has the property to absorb moisture. Hence it is used as a... View Article

An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change? (a) Baking powder (b) Lime (c) Ammonium hydroxide solution (d) Hydrochloric acid

Answer: (d) Hydrochloric acid If the solution turns red litmus to blue colour then the solution should be basic in nature. Its effect can be... View Article

What happens when a solution of an acid is mixed with a solution of a base in a test tube? (i) The temperature of the solution increases (ii) The temperature of the solution decreases (iii) The temperature of the solution remains the same (iv) Salt formation takes place (a) (i) only (b) (i) and (iii) (c) (ii) and (iii) (d) (i) and (iv)

Answer: (d) (i) and (iv) When acid is mixed with a solution of base it results in a neutralization reaction. Neutralization is an exothermic... View Article

You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO₃, ZnCl₂ and H₂O. In which of the above containers these solutions can be kept?

Answer: These solutions can be kept in a copper container because copper is a noble metal which will not react with HCl or even HNO3. If we keep... View Article

On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, a white precipitate is obtained. (a) Write a balanced chemical equation of the reaction involved (b) What other names can be given to this precipitation reaction? (c) On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?

Answer: (a) On adding a drop of Barium Chloride solution to an aqueous solution of sodium sulphite, barium sulphite is obtained which is white... View Article

What happens when zinc granules are treated with a dilute solution of H2SO4, HCl, HNO3, NaCl and NaOH, also write the chemical equations if a reaction occurs.

Answer: When Zinc granules react with dil H2SO4 displacement reaction takes place leading to the formation of ZnSO4 liberating H2 gas Zn(s)+... View Article

What happens when a piece of silver metal is added to copper sulphate solution? Also, write the balanced chemical equation if the reaction occurs

Answer: When silver metal is added to copper sulphate solution there will not be any reaction as silver is non-reactive metal. As per the metals,... View Article

What happens when a piece of aluminium metal is added to dilute hydrochloric acid? Also, write the balanced chemical equation if the reaction occurs

Answer: Aluminum reacts with diluted hydrochloric acid at room temperature. The metal aluminium... View Article

What happens when a piece of zinc metal is added to copper sulphate solution? Also, write the balanced chemical equation if the reaction occurs

Answer: When zinc is added to copper sulphate (CuSO4) solution due to more reactivity of zinc, cooper is replaced by the zinc and forms zinc... View Article

Give the characteristic tests for the following gases (a) CO2 (b) SO2 (c) O2 (d) H2

Answer: Limewater is basically a solution of calcium hydroxide. So if we bubble carbon dioxide through the solution it reacts with calcium... View Article

A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining. (a) Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved. (b) Name the black substance formed and give its chemical formula.

Answer: (a) There are traces of hydrogen sulphide (H2S) gas in the air. Silver sulphide is formed as H2S slowly reacts with the silver in the... View Article

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