This question is about compounds - AQA - GCSE Chemistry - Question 5 - 2015 - Paper 2

A soluble compound that contains carbonate ions is potassium carbonate, represented by the formula K₂CO₃, or sodium carbonate, represented by Na₂CO₃.

A metal oxide is typically classified as a base, which can react with acids to produce salts.

Solid lead nitrate can be obtained from lead nitrate solution through evaporation or crystallization.

The balanced equation for the reaction is:

The formula Pb(NO₃)₂ contains a total of 9 atoms: 1 lead (Pb), 2 nitrogen (N), and 6 oxygen (O) atoms.

First, we find the number of moles of lead and oxygen:

• Moles of Pb = ( \frac{6.21}{207} \approx 0.03 )
• Moles of O = ( \frac{0.72}{16} \approx 0.045 )

Now, dividing both by the smaller number of moles (0.03):

• Pb: ( \frac{0.03}{0.03} = 1 )
• O: ( \frac{0.045}{0.03} = 1.5 )

Converting to whole numbers gives us a ratio of 2:3.

Thus, the empirical formula of the lead oxide is Pb₂O₃.