Chapter 1: Chemical reactions and equations

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Chemical reactions and equations

Question:

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.

(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Answer:

(a) The hydrogen gas reacts with nitrogen gas to form ammonia gas. The chemical equation for this reaction is written as:

H2 (g) + N2 (g) → NH3 (g)

The number of atoms of different elements present in the given unbalanced equation is as follows:

First balance hydrogen by multiply 3 in the reactant side and 2 in the product side as shown below:

3 H2 (g) + N2 (g) → 2 NH3 (g)

The number of atoms of different elements present in the given balanced equation is as follows:

Therefore, the correct answer is 3H2(g)+N2(g)→2NH3(g).

 

(b) Hydrogen sulphide gas reacts with oxygen gas to form sulphur dioxide gas along with water. The chemical equation for this reaction is written as:

H2S (g) + O2 (g) → SO2 (g) + H2O (l)

The number of atoms of different elements present in the given unbalanced equation is as follows:

First balance oxygen by multiply 3 in the reactant side and 2 in the product side as shown below:

H2S (g) + 3 O2 (g) → 2 SO2 (g) + 2 H2O (l)

Now, balance hydrogen by multiply 2 in the reactant side as shown below:

2 H2S (g) + 3 O2 (g) → 2 SO2 (g) + 2 H2O (l)

The number of atoms of different elements present in the given balanced equation is as follows:

Therefore, the correct answer is 2H2S(g)+3O2(g)→2SO2(g)+2H2O(l).

 

(c) The chemical equation for this reaction is written as:

BaCl2 (aq) + Al2(SO4)3 (aq) → AlCl3 (aq) + BaSO4 (s)

The number of atoms of different elements present in the given unbalanced equation is as follows:

First balance oxygen by multiply 3 in the product side as shown below:

BaCl2 (aq) + Al2(SO4)3 (aq) → AlCl3 (aq) + 3 BaSO4 (s)

Now, balance barium by multiply 3 in the reactant side.

3 BaCl2 (aq) + Al2(SO4)3 (aq) → AlCl3 (aq) + 3 BaSO4 (s)

The aluminium atom is balanced by multiplying 2 in the product side as shown below.

3 BaCl2 (aq) + Al2(SO4)3 (aq) → 2 AlCl3 (aq) + 3 BaSO4 (s)

The number of atoms of different elements present in the given balanced equation is as follows:

Therefore, the correct answer is 3 BaCl2 (aq) + Al2(SO4)3 (aq) → 2 AlCl3 (aq) + 3 BaSO4 (s).

 

(d) The chemical equation for this reaction is written as:

K (s) + H2O (l) → KOH (aq) + H2 (g)

The number of atoms of different elements present in the given unbalanced equation is as follows:

First, balance hydrogen by multiply 2 in the reactant side and 2 in the product side as shown below:

K (s) + 2 H2O (l) → 2 KOH (aq) + H2 (g)

The potassium atom is balanced by multiply 2 in the reactant side.

2 K (s) + 2 H2O (l) → 2 KOH (aq) + H2 (g)

The number of atoms of different elements present in the given balanced equation is as follows:

Therefore, the correct answer is 2 K(s)+2H2O(l)→2KOH(aq)+H2(g).


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