Question 7.1 [2 marks]
A Lowry-Brønsted base is defined as a species that can accept a proton (H⁺ ion) from another species during a chemical reaction. In essence, it acts as a proton acceptor.
Question 7.2 [6 marks]
The reaction can be rewritten as follows, with the conjugate acid-base pairs indicated:
\[ \text{HSO}_4^- + \text{HCO}_3^- \rightarrow \text{SO}_4^{2-} + \text{H}_2\text{CO}_3 \]
Conjugate Acid-Base Pairs:
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For the forward reaction:
- HSO₄⁻ (acid) ⇔ SO₄²⁻ (conjugate base)
- HCO₃⁻ (base) ⇔ H₂CO₃ (conjugate acid)
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For the reverse reaction:
- SO₄²⁻ (base) ⇔ HSO₄⁻ (conjugate acid)
- H₂CO₃ (acid) ⇔ HCO₃⁻ (conjugate base)
You may highlight or use color coding to make the pairs stand out, for instance:
- Red for acids (HSO₄⁻, H₂CO₃)
- Blue for bases (SO₄²⁻, HCO₃⁻)
Question 7.3 [2 marks]
The ampholytes in the reaction are:
- HSO₄⁻ (hydrogen sulfate ion) - It can act as either an acid or a base depending on the reaction conditions.
- HCO₃⁻ (bicarbonate ion) - It can also act as either an acid or a base depending on the reaction conditions.
Question 7.4 [3 marks]
The balanced chemical equation for the reaction when magnesium oxide (MgO) reacts with nitric acid (HNO₃) is:
\[ \text{MgO} + 2 \text{HNO}_3 \rightarrow \text{Mg(NO}_3\text{)}_2 + \text{H}_2\text{O} \]
Question 7.5 [incomplete]
Given that you mentioned 50 g of IMPURE calcium carbonate reacts with 200 cm³ of a dilute sulfuric acid with a concentration of 1.5 mol∙dm⁻³, you may need to proceed with these steps to solve the problem:
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Determine moles of sulfuric acid: \[ \text{Volume of H₂SO₄} = 200 , \text{cm}^3 = 0.200 , \text{dm}^3 \] \[ \text{Moles of H₂SO₄} = \text{Concentration} \times \text{Volume} = 1.5 , \text{mol/dm}^3 \times 0.200 , \text{dm}^3 = 0.3 , \text{mol} \]
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Balanced reaction with calcium carbonate (CaCO₃): The balanced reaction for calcium carbonate with sulfuric acid is: \[ \text{CaCO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{CaSO}_4 + \text{H}_2\text{O} + \text{CO}_2 \]
From this equation, you can see that 1 mole of CaCO₃ reacts with 1 mole of H₂SO₄.
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Determine how many moles of CaCO₃ could react with sulfuric acid using the 0.3 moles of H₂SO₄: Therefore, 0.3 moles of H₂SO₄ will react with 0.3 moles of CaCO₃.
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Use the molar mass to find the mass of CaCO₃: The molar mass of CaCO₃ is approximately 100.09 g/mol. \[ \text{Mass of CaCO}_3 = \text{moles} \times \text{molar mass} = 0.3 , \text{mol} \times 100.09 , \text{g/mol} \approx 30.03 , \text{g} \]
So if 30.03 g of calcium carbonate reacts, you can find the purity or impurities accordingly in the 50 g sample. However, since the question was incomplete, further details from that section would be helpful for the final steps.
1 answer