A student prepared 20% sodium hydroxide solution in a beaker containing water. The observations noted by him are given below. (1)

I. Sodium hydroxide is in the form of pellets.

II. It dissolves in water readily.

III. The beaker appears cold when touched from outside.

IV. The red litmus paper turns blue when dipped into the solution.

The correct observations are:

(A) I, II, and III

(B) II, III and IV

(C) III, IV and I

(D) I, II and IV

A student prepared 20% sodium hydroxide solution in a beaker containing water. The observations noted by him are given below. (1)

I. Sodium hydroxide is in the form of pellets.

II. It dissolves in water readily.

III. The beaker appears cold when touched from outside.

IV. The red litmus paper turns blue when dipped into the solution.

The correct observations are:

(A) I, II, and III

(B) II, III and IV

(C) III, IV and I

(D) I, II and IV

A student prepared 20% sodium hydroxide solution in a beaker containing water. The observations noted by him are given below. (1)

I. Sodium hydroxide is in the form of pellets.

II. It dissolves in water readily.

III. The beaker appears cold when touched from outside.

IV. The red litmus paper turns blue when dipped into the solution.

The correct observations are:

(A) I, II, and III

(B) II, III and IV

(C) III, IV and I

(D) I, II and IV

Solutions of copper sulphate, iron sulphate and zinc sulphate are prepared and marked I, II and III respectively. Few pieces of aluminium are added to each solutions. After some time a change will be observe in

(A) I and II

(B) II and III

(C) III and I

(D) All the three

A student prepared an aqueous solution of CuSO₄ in beaker X and an aqueous solution of FeSO₄ in beaker Y. He then dropped some iron pieces in beaker X and some zinc pieces in beaker Y. After about 10 hours he observed that the solutions in X and Y respectively appear:

(A) blue and green

(B) colourless and pale green

(C) colourless and light blue

(D) greenish and colourless

A student prepared an aqueous solution of CuSO₄ in beaker X and an aqueous solution of FeSO₄ in beaker Y. He then dropped some iron pieces in beaker X and some zinc pieces in beaker Y. After about 10 hours he observed that the solutions in X and Y respectively appear:

(A) blue and green

(B) colourless and pale green

(C) colourless and light blue

(D) greenish and colourless

To show that zinc is a more active metal than copper, the correct procedure is to: 

(1) add dilute nitric acid on strips of both the metals. 

(2) observe transmission of heat through strips of zinc and copper. 

(3) prepare solution of zinc sulphate and hang strip of copper into it. 

(4) prepare solution of copper sulphate and hang strip of zinc into it. 

Write any two observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer.

No chemical reaction takes place when granules of a solid, A, are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C, is a metal and settles down in the molten state while the other product, D, floats over it. It was observed that the reaction is highly exothermic.

(i) Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and thermal status of reaction.

(ii) Mention any two types of reactions under which above chemical reaction can be classified.

(i) What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube?

(ii) What type of reaction is this?

(iii) Write a balanced chemical equation to represent the above reaction.

In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?

Write the name and chemical formula of the calcium compound used for disinfecting drinking water. How is this compound manufactured?

(i) What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube?

(ii) What type of reaction is this?

(iii) Write a balanced chemical equation to represent the above reaction.

(a) What is vinegar?

(b) Describe with a chemical equation, what happens when sodium hydrogen carbonate reacts with ethanoic acid.

Name a reducing agent that may be used to obtain manganese from manganese dioxide.

Define a combination reaction. Give one example of a combination reaction which is also exothermic.

What is an oxidation reaction? Give an example of oxidation reaction. Is oxidation an exothermic or an endothermic reaction?

In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?

(i) Name the products formed when sodium hydrogen carbonate is heated.

(ii) Write the chemical equation for the reaction involved in the above.

(i) What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube?

(ii) What type of reaction is this?

(iii) Write a balanced chemical equation to represent the above reaction.

In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?

Write the chemical formula for washing soda. How may it be obtained from baking soda? Name an industrial use of washing soda other than washing clothes.

Give an example of a decomposition reaction. Describe an activity to illustrate such a reaction by heating.

Write the chemical formula for bleaching powder. How is bleaching powder prepared? For what purpose is it used in paper factories?

Classify the following reactions into slow and fast reaction:

(i) Reaction between an acid and a base

(ii) Rusting of iron

(a) Write the chemical name and formula of bleaching powder.

(b) Why does bleaching powder smell of chlorine when exposed to air?

(c) Write chemical equation to represent the action of dilute hydrochloric acid on bleaching powder.

(i) Name the raw materials used in the manufacture of sodium carbonate by Solvay process.

(ii) How is the sodium hydrogen carbonate formed during Solvay process separated from a mixture of NH₄Cl and NaHCO₃?

(iii) How is sodium carbonate obtained from sodium hydrogen carbonate?

State a reaction in which SO₂ acts as an oxidising agent.

(a) State the relation between hydrogen ion concentration of an aqueous solution and its pH.
(b) The pH of an aqueous solution decreases from 3 to 2. Calculate how many times the hydrogen ion concentration of the solution will change.

(a) Why is ZnO called an amphoteric oxide? Name another amphoteric oxide.

(b) What are alkalies? Give one example of alkalies. 

What is observed when a mixture of hydrogen and chlorine is exposed to sunlight? What is the product formed?