Chemguide: Core Chemistry 14 - 16

Answers to Set 4 of the equations problems

Word equation:

potassium + water    potassium hydroxide + hydrogen

Convert to symbols:

K + H₂O    KOH + H₂

Everything else is OK but you have got one too many hydrogen atoms on the right-hand side - so have half of an H₂ molecule.

K + H₂O    KOH + ½H₂

Balanced equation:

2K + 2H₂O    2KOH + H₂

Word equation:

iron(III) oxide + nitric acid (HNO₃)    iron(III) nitrate + water

Convert to symbols:

Fe₂O₃ + HNO₃    Fe(NO₃)₃ + H₂O

This is simple enough to balance as long as you do things in the right order. Start with the iron, then the nitrate groups and then the hydrogens. You will find that the oxygens sort themselves out.

Balanced equation:

Fe₂O₃ + 6HNO₃    2Fe(NO₃)₃ + 3H₂O

Word equation:

barium chloride + potassium sulfate    barium sulfate + potassium chloride

Convert to symbols:

BaCl₂ + K₂SO₄    BaSO₄ + KCl

Balanced equation:

BaCl₂ + K₂SO₄    BaSO₄ + 2KCl

Word equation:

magnesium + sulfuric acid (H₂SO₄)    magnesium sulfate + hydrogen

Convert to symbols:

Mg + H₂SO₄    MgSO₄ + H₂

Balanced equation:

The equation is already balanced.

Word equation:

sodium + oxygen    sodium oxide

Convert to symbols:

Na + O₂    Na₂O

Balance the sodiums first:

2Na + O₂    Na₂O

Now lose an oxygen on the left-hand side by having half an oxygen molecule . . .

2Na + ½O₂    Na₂O

. . . and double everything.

Balanced equation:

4Na + O₂    2Na₂O

Return to the problems . . .