Lithium, sodium and potassium are reactive metals in group 1 of the periodic table - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2018 - Paper 1
Question 6
Lithium, sodium and potassium are reactive metals in group 1 of the periodic table.
(a) Sodium metal tarnishes in air to form a layer of sodium oxide on its surface... show full transcript
Worked Solution & Example Answer:Lithium, sodium and potassium are reactive metals in group 1 of the periodic table - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2018 - Paper 1
Step 1
Calculate the number of moles of sodium and oxygen
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Answer
To calculate the number of moles of each element, use the formula:
ext{Number of moles} = rac{ ext{mass}}{ ext{molar mass}}
For sodium (Na):
ext{Moles of Na} = rac{0.92 ext{ g}}{23 ext{ g/mol}} = 0.04 ext{ mol}
For oxygen (O):
ext{Moles of O} = rac{0.32 ext{ g}}{16 ext{ g/mol}} = 0.02 ext{ mol}
Step 2
Determine the simplest mole ratio
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Answer
Next, divide both mole values by the smaller number of moles:
For Na:
rac{0.04 ext{ mol}}{0.02 ext{ mol}} = 2
For O:
rac{0.02 ext{ mol}}{0.02 ext{ mol}} = 1
This gives a ratio of sodium to oxygen as 2:1.
Step 3
State the empirical formula
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Answer
The empirical formula of sodium oxide is therefore:
extNa2extO
Step 4
Complete the balanced equation with state symbols
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The balanced chemical equation for the reaction of sodium with water is:
ightarrow 2 ext{NaOH}(aq) + ext{H}_2(g) $$
Here, (s) stands for solid, (l) for liquid, (aq) for aqueous, and (g) for gas.
