GCSE Edexcel Chemistry Group 1 – Alkali metals: Lithium, sodium and potassium ar

Lithium, sodium and potassium are reactive metals in group 1 of the periodic table - Edexcel - GCSE Chemistry - Question 3 - 2018 - Paper 1

Question 3

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 3 - 2018 - Paper 1

Step 1

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 formula of this sodium oxide.

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Answer

To calculate the empirical formula, we first need to determine the number of moles of sodium and oxygen.

Calculate Moles:
- Moles of Sodium (Na): $\frac{0.92 ext{ g}}{23 ext{ g/mol}} = 0.04 ext{ mol}$
- Moles of Oxygen (O): $\frac{0.32 ext{ g}}{16 ext{ g/mol}} = 0.02 ext{ mol}$
Determine Ratio:
- Ratio of Na to O:
- Divide both by the smaller number of moles:
- For Na: $\frac{0.04}{0.02} = 2$
- For O: $\frac{0.02}{0.02} = 1$
Write Empirical Formula: The empirical formula for sodium oxide is $\text{Na}_2\text{O}$ .

Step 2

Sodium reacts with water to form sodium hydroxide solution and hydrogen. Complete the balancing of the equation for this reaction and add the state symbols for each substance.

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Answer

The balanced equation for the reaction is:

$2 \text{Na (s)} + 2 \text{H}_2\text{O (l)} \rightarrow 2 \text{NaOH (aq)} + \text{H}_2 (g)$

Step 3

In an experiment equal-sized pieces of lithium, sodium and potassium are added to separate samples of water. A flame is produced only with potassium because potassium

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Answer

C is the most reactive.

Step 4

Explain, in terms of electronic configurations, the increase in reactivity from lithium to sodium to potassium.

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Answer

The increase in reactivity from lithium to sodium to potassium can be explained by their electronic configurations.

Lithium (Li) has the electronic configuration $1s^2 2s^1$ with one electron in its outer shell.
Sodium (Na) has the configuration $1s^2 2s^2 2p^6 3s^1$ , also having one outer electron in a higher energy shell.
Potassium (K) has the configuration $1s^2 2s^2 2p^6 3s^2 3p^6 4s^1$ , with one outer electron in even higher energy.

As you move down the group, the outer electron is further from the nucleus, leading to lower ionization energy and therefore increased reactivity.

Lithium, sodium and potassium are reactive metals in group 1 of the periodic table - Edexcel - GCSE Chemistry - Question 3 - 2018 - Paper 1

Worked Solution & Example Answer:Lithium, sodium and potassium are reactive metals in group 1 of the periodic table - Edexcel - GCSE Chemistry - Question 3 - 2018 - Paper 1

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 formula of this sodium oxide.

Sodium reacts with water to form sodium hydroxide solution and hydrogen. Complete the balancing of the equation for this reaction and add the state symbols for each substance.

In an experiment equal-sized pieces of lithium, sodium and potassium are added to separate samples of water. A flame is produced only with potassium because potassium

Explain, in terms of electronic configurations, the increase in reactivity from lithium to sodium to potassium.

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