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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 surfa... 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
Calculate the empirical formula of sodium oxide
Answer
To find the empirical formula, we first need to determine the number of moles of each element in the compound.
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Calculate the moles of sodium (Na):
To simply this, we use:
Moles of sodium = \frac{0.92g}{23g/mol} = 0.04 ext{ moles}
Moles of oxygen = \frac{0.32g}{16g/mol} = 0.02 ext{ moles}
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Determine the mole ratio by dividing both variables by the smaller number (0.02):
- Sodium: 0.04 / 0.02 = 2
- Oxygen: 0.02 / 0.02 = 1
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Therefore, the empirical formula is (Na_2O).
Step 2
Complete the equation for sodium reacting with water
Answer
The balanced equation for sodium reacting with water to produce sodium hydroxide and hydrogen is:
[ 2Na (s) + 2H_2O (l) \rightarrow 2NaOH (aq) + H_2 (g) ]
Each substance and its state symbol:
- Sodium (Na): (s)
- Water (H2O): (l)
- Sodium Hydroxide (NaOH): (aq)
- Hydrogen (H2): (g)
Step 3
Step 4
Explain, in terms of electronic configurations, the increase in reactivity from lithium to sodium to potassium
Answer
The increase in reactivity from lithium (Li) to sodium (Na) to potassium (K) can be explained by the following:
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Electronic Configuration:
- Lithium has an electronic configuration of 1s² 2s¹, meaning it has one electron in its outer shell.
- Sodium has an electronic configuration of 1s² 2s² 2p⁶ 3s¹, with one outer electron as well.
- Potassium has the configuration of 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹, again having one outer electron.
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Increased Atomic Size:
As we move down the group, the atomic radius increases. This means the outermost electron is further from the nucleus, which results in less effective nuclear attraction. -
Lower Ionization Energy:
The energy required to remove the outer electron decreases from lithium to sodium to potassium, indicating greater reactivity.
Therefore, potassium is the most reactive among the three.