Photo AI
Sodium metal tarnishes in air to form a layer of sodium oxide on its surface - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2018 - Paper 1
Question 6
Sodium metal tarnishes in air to form a layer of sodium oxide on its surface. 0.92 g of sodium combined with 0.32 g of oxygen in this oxide. Calculate the empirical... show full transcript
Worked Solution & Example Answer:Sodium metal tarnishes in air to form a layer of sodium oxide on its surface - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2018 - Paper 1
Step 1
Calculate the empirical formula of sodium oxide.
Answer
-
Calculate moles of sodium and oxygen:
- Moles of sodium = ( \frac{0.92 ext{ g}}{23 ext{ g/mol}} = 0.04 \text{ mol} )
- Moles of oxygen = ( \frac{0.32 ext{ g}}{16 ext{ g/mol}} = 0.02 \text{ mol} )
-
Find the simplest mole ratio:
- Divide the number of moles by the smallest value (0.02):
- Sodium: ( \frac{0.04}{0.02} = 2 )
- Oxygen: ( \frac{0.02}{0.02} = 1 )
-
Empirical formula:
- The ratio of sodium to oxygen is 2:1, so the empirical formula is ( ext{Na}_2 ext{O} ).
Step 2
Complete the balancing of the equation for this reaction and add the state symbols.
Answer
-
Write the unbalanced equation:
[ ext{Na} + 2 ext{H}_2 ext{O} \rightarrow ext{NaOH} + ext{H}_2 ] -
Identify state symbols:
- Sodium (Na) is solid: (s)
- Water (H2O) is liquid: (l)
- Sodium hydroxide (NaOH) is aqueous: (aq)
- Hydrogen (H2) is gas: (g)
-
Final balanced equation with state symbols:
[ 2 ext{Na}(s) + 2 ext{H}_2 ext{O}(l) \rightarrow 2 ext{NaOH}(aq) + ext{H}_2(g) ]