Observations That Help Determine Chemical Change

Q.

Which type of reaction takes place when an iron nail is dipped in a solution of copper sulphate?

1. Combination

2. Displacement

3. Double displacement

4. Decomposition

Q.

Question 13
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice.

Explain why these sour substances are effective in cleaning the vessels.

Q. gas is released when iron filings react with hydrochloric acid.

1. Hydrogen
2. Oxygen
3. Chlorine

Q.

When an acid reacts with a metal carbonate or metal hydrogen carbonate, it gives the corresponding salt, gas and product. Name the gas and product?

1. Hydrogen and salt

2. Carbon dioxide and salt

3. Carbon dioxide and water

4. Only carbon dioxide

Q. Which amongst the following observations does not indicate that a chemical reaction has occurred?

1. Change in total mass of substance
2. Production of gas
3. Formation of a precipitate
4. Evolution of heat and light

Q.

Which of the following gas is formed when copper reacts with a hot dilute nitric acid?

1. N₂O₅

2. NO₂

3. N₂O

4. NO

Q.

Which of the following parameters of a substance does not alter during a physical change?

1. Size

2. Mass

3. State

4. Volume

Q.

_________.deals with the study of matter and the changes it undergoes .

Q.

Which of the following is a physical change and which is a chemical change? Explain

(i) Wool being knitted into a sweater

(ii) Coal being burnt in air

(iii) Melting of butter in a pan

(iv) Cutting of trees

(v) Dissolving of sugar in water

Q.

State one instance where water undergoes physical change and one in which it undergoes a chemical change.

Q. Copper sulphate solution isin colour. If iron filings are added to it, the colour changes to.

1. orange
2. blue
3. red
4. green
5. black

Q. We can show that iron is more reactive than copper :
(1) by preparing copper sulphate solution and dipping iron strip in it
(2) by dipping both the strips in water for some time
(3) by preparing iron sulphate solution and dipping copper strip in it
(4) by heating both iron and copper strips

Q. Gas is evolved in which of the chemical reaction?
[1mark]
A. Zinc reacting with dilute sulphuric acid
B. Iron dropped into copper sulphate solution.
C. Silver Nitrate is added to a Sodium Chloride solution.
D. Ammonia Gas reacting with Hydrochloric Acid.

Q.

Nitrogen of the air enters the soil as nitric acid. Give balance equation to show the conversion of nitrogen to nitric acid.

Q.

1. Name the process by which nitric acid is obtained on a large scale.
2. Name the reactant used.
3. (i) Name the catalyst used. (ii) Upto what temperature is the catalyst heated. (iii) Give the reaction taking place in the catalytic chamber. (iv) Name the products formed.

Q. Why is direct sunlight not used in the preparation of hydrogen chloride gas?

1. Reaction is explosive in direct sunlight.
2. Reaction is slow in direct sunlight.
3. None of these
4. There is no reaction in direct sunlight.

Q.

What are the possible changes in a chemical reaction?

1. Evolution of gas

2. Change in Colour

3. Formation of Precipitate

4. A new element is formed

Q. Burning of wax is achange and melting of wax is achange.

1. chemical
2. mechanical
3. biological
4. physical

Q. When the stopper of a bottle full of hydrogen chloride gas is opened, fumes can be seen coming out. Why does this happen?

1. Hydrogen is a noble gas
2. There is immediate reaction between HCL and water vapour in the air.
3. It reacts with the bottle to release fumes.
4. None of these

Q. Identify the substance(s) which can be separated as pure crystals from the impure samples.
1. Copper sulphate
2. Potassium nitrate
3. Ferrous sulphate

1. Only 1
2. Only 1 and 2
3. All 1, 2 and 3
4. Only 3

Q. What happens when sulphuric acid reacts with zinc metal?

Q.

Which of the following observations helps to determine whether a chemical reaction has taken place or not?

(i) Change in state.

(ii) Change in colour.

(iii) Change in shape

(iv) Evolution of gas.

(v) Change in temperature.

1. (ii), (iii), (iv), (v)

2. (i), (ii), (iv), (v)

3. (i), (ii), (iii), (v)

4. (iii), (v)

Q. A dilute solution of sodium carbonate was added to two test tubes - one containing dilute $HCl$ (A) and the other containing dilute $NaOH$ (B). The correct observation was

1. A brown coloured gas liberated in test tube A.
2. A brown coloured gas liberated in test tube B.
3. A colourless gas liberated in test tube A.
4. A colourless gas liberated in test tube B.

Q. Observing the changes, in which of the following would you say a chemical reaction may be occurring?
(i) Heating iodine changes the colour from bluish black to purple
(ii) Mixing ammonia and hydrogen chloride gases gives fumes containing a white powdery substance
(iii) Mixing an acid and a base solution raises the temperature.
(iv) Mixing ferrous sulphide and hydrochloric acid gives off a gas with a rotten egg smell

1. (i), (ii), (iii), (iv)
2. (ii), (iii), (iv)
3. (i), (ii), (iii)
4. (i), (ii), (iv)

Q.

what is the relationship between hydrochloric acid and zinc?

Q.

White silver chloride in sunlight turns to

1. red

2. grey

3. yellow

4. remain white

Q.

Gas is evolved in which of the chemical reaction?

1. Zinc reacting with dilute sulphuric acid

2. Iron dropped into copper sulphate solution.

3. Silver Nitrate is added to a Sodium Chloride solution.

4. Ammonia Gas reacting with Hydrochloric Acid.

Q.

Name the gas released: 1. Zinc+Sulphuric acid

2. Manganese dioxide+ Hydrochloric acid

3. Sodium sulphide+Dilute sulphuric acid

4. Sodium carbonate+Hydrochloric acid

Q. Which of these suggest that a chemical reaction may be occurring?

1. Change of colour
2. Change of state
3. Reduction of temperature
4. Release of a gas

Q. gas is released when iron filings react with hydrochloric acid.

1. Hydrogen
2. Oxygen
3. Chlorine