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Lithium, sodium and potassium are reactive metals in group 1 of the periodic table - Edexcel - GCSE Chemistry - Question 9 - 2018 - Paper 1
Question 9
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 - Question 9 - 2018 - Paper 1
Step 1
Sodium Oxide Empirical Formula Calculation
Answer
To find the empirical formula, we first determine the number of moles of sodium (Na) and oxygen (O).
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Calculate the moles of sodium:
Moles of Na = mass of Na / atomic mass of Na = ( \frac{0.92 ext{ g}}{23 ext{ g/mol}} \approx 0.04 ext{ moles} )
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Calculate the moles of oxygen:
Moles of O = mass of O / atomic mass of O = ( \frac{0.32 ext{ g}}{16 ext{ g/mol}} \approx 0.02 ext{ moles} )
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Determine the simplest mole ratio:
- Ratio of Na to O = ( \frac{0.04}{0.02} : \frac{0.02}{0.02} = 2:1 )
The empirical formula is ( Na_2O ).
Step 2
Complete the equation and state symbols
Answer
The balanced equation for the reaction of sodium with water is:
Na( s ) + 2H2O( l ) → NaOH( aq ) + H2( g )
- Na (s) indicates solid sodium.
- H2O (l) indicates liquid water.
- NaOH (aq) indicates sodium hydroxide in aqueous solution.
- H2 (g) indicates hydrogen gas.