Question

1. neatly & clearly complete the following equations: (4 marks each)

sodium oxide + water → sodium hydroxide_(aq)
skeleton:
balanced:

iron (iii) + hydrofluoric acid → hydrogen gas + iron (iii) fluoride_(aq)
skeleton:
balanced:

sulfuric acid + barium hydroxide_(aq) → water + barium sulfate_(s)
skeleton:
balanced:

1. balance the following chemical equations: (2 marks each)

c_3h_8(g) + o_2(g) → co_2(g) + h_2o(g)
bacl_2(aq) + k_3po_4(aq) → kcl(aq) + ba_3(po_4)_2(s)

Explanation:

Step1: Write skeleton equations

1. For sodium oxide + water → sodium hydroxide:

• The skeleton equation is \(Na_2O + H_2O

ightarrow NaOH\).

1. For iron (III) + hydrofluoric acid → hydrogen gas + iron (III) fluoride:

• The skeleton equation is \(Fe+HF

ightarrow H_2 + FeF_3\).

1. For sulfuric acid + barium hydroxide → water + barium sulfate:

• The skeleton equation is \(H_2SO_4 + Ba(OH)_2

ightarrow H_2O+BaSO_4\).

1. For \(C_3H_8 + O_2

ightarrow CO_2 + H_2O\), it is already in skeleton - form.

1. For \(BaCl_2+K_3PO_4

ightarrow KCl + Ba_3(PO_4)_2\), it is already in skeleton - form.

Step2: Balance the equations

1. For \(Na_2O + H_2O

ightarrow NaOH\):

• There are 2 sodium atoms on the left - hand side. So, we need 2 moles of \(NaOH\) on the right - hand side. The balanced equation is \(Na_2O + H_2O = 2NaOH\).

1. For \(Fe+HF

ightarrow H_2 + FeF_3\):

• First, balance the fluorine atoms. We need 3 moles of \(HF\) to get 3 moles of \(F\) atoms. Then, to balance the hydrogen atoms, we need \(\frac{3}{2}\) moles of \(H_2\). Multiply through by 2 to get whole numbers. The balanced equation is \(2Fe + 6HF=3H_2 + 2FeF_3\).

1. For \(H_2SO_4 + Ba(OH)_2

ightarrow H_2O+BaSO_4\):

• The number of \(H\), \(S\), \(O\) and \(Ba\) atoms on both sides is already equal when we consider the products and reactants directly. The balanced equation is \(H_2SO_4 + Ba(OH)_2 = 2H_2O+BaSO_4\).

1. For \(C_3H_8 + O_2

ightarrow CO_2 + H_2O\):

• First, balance the carbon atoms. We need 3 moles of \(CO_2\) for 3 carbon atoms in \(C_3H_8\). Then, balance the hydrogen atoms. There are 8 hydrogen atoms in \(C_3H_8\), so we need 4 moles of \(H_2O\). Finally, balance the oxygen atoms. On the right - hand side, we have \(3\times2 + 4\times1=10\) oxygen atoms. So, we need 5 moles of \(O_2\) on the left - hand side. The balanced equation is \(C_3H_8+5O_2 = 3CO_2 + 4H_2O\).

1. For \(BaCl_2+K_3PO_4

ightarrow KCl + Ba_3(PO_4)_2\):

• First, balance the barium atoms. We need 3 moles of \(BaCl_2\). Then, balance the potassium atoms. We need 6 moles of \(KCl\). The balanced equation is \(3BaCl_2 + 2K_3PO_4=6KCl + Ba_3(PO_4)_2\).

Answer:

1. Skeleton: \(Na_2O + H_2O

ightarrow NaOH\); Balanced: \(Na_2O + H_2O = 2NaOH\)

1. Skeleton: \(Fe+HF

ightarrow H_2 + FeF_3\); Balanced: \(2Fe + 6HF=3H_2 + 2FeF_3\)

1. Skeleton: \(H_2SO_4 + Ba(OH)_2

ightarrow H_2O+BaSO_4\); Balanced: \(H_2SO_4 + Ba(OH)_2 = 2H_2O+BaSO_4\)

1. Skeleton: \(C_3H_8 + O_2

ightarrow CO_2 + H_2O\); Balanced: \(C_3H_8+5O_2 = 3CO_2 + 4H_2O\)

1. Skeleton: \(BaCl_2+K_3PO_4

ightarrow KCl + Ba_3(PO_4)_2\); Balanced: \(3BaCl_2 + 2K_3PO_4=6KCl + Ba_3(PO_4)_2\)