Observations of Chemical Changes

Q.

Translate the following statements into chemical equations and then balance them.

(A) Hydrogen gas combines with nitrogen to form ammonia

(B) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

(C) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. [3 MARKS]

Q. Identify the gas evolved during the burning​​
of wood.​​

1. Oxygen​​
2. Nitrogen​​
3. Hydrogen​​
4. Carbon dioxide​​

Q.

Which of the following changes indicate that a chemical change has not been taken place?

1. No new substance is formed
2. Change in colour
3. Absorption or release of heat
4. Evolution of gas

Q. Complete the equation:
$CuS{O}_4$(aq) +2 $N{H}_{4}OH$(aq)$\to$(blue ppt) + $(N{H}_4{)}_{2}S{O}_4$(aq)

1. $\mathrm{Cu}(\mathrm{OH}{)}_2$
2. $C{u}_{2}O$
3. CuO

Q. Match the correct pairs.

1. 
2. 
3. 
4. 
5. 
6. 

Q.

Which of the following changes indicate that a chemical change has not been taken place?

1. No new substance is formed
2. Absorption or release of heat
3. Change in colour
4. Evolution of gas

Q. is the catalyst used in the reaction $2H_2{O}_2\to 2H_{2}O+O_2$

1. ${\mathrm{CuSO}}_4$
2. ${\mathrm{FeSO}}_4$
3. ${\mathrm{NH}}_4\mathrm{OH}$

Q. While burning a candle, the melting of wax is a change whereas the burning of wick is a change.

1. physical
2. chemical
3. periodic
4. natural

Q. When ferrous sulphate $\left({\text{FeSO}}_4\right)$ solution combines with sodium hydroxide $\text{(NaOH)}$, the chemical change is identified by the .

1. formation of gas
2. formation of ppt
3. absoprtion of heat