Equal volumes of four 0.1 mol L\(^{-1}\) acids were titrated with the same sodium hydroxide solution.
Which one requires the greatest volume of base to change the colour of the indicator?
- Citric acid
- Acetic acid
- Sulfuric acid
- Hydrochloric acid
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Equal volumes of four 0.1 mol L\(^{-1}\) acids were titrated with the same sodium hydroxide solution.
Which one requires the greatest volume of base to change the colour of the indicator?
\(A\)
→ Citric acid is triprotic.
→ Sulfuric acid is diprotic.
→ Acetic acid and Hydrochloric acid are monoprotic.
→ The greatest volume of \(\ce{NaOH}\) is required for the triprotic acid as it has a 1:3, acid:base, stoichiometric ratio.
\(\Rightarrow A\)
A household cleaning agent contains a weak base with the formula \( \ce{NaX}\). 1.00 g of this compound was dissolved in water to give 100.0 mL of solution. A 20.0 mL sample of the solution was titrated with 0.100 mol L\(^{-1}\) hydrochloric acid, and required 24.4 mL of the acid for neutralisation.
What is the molar mass of the weak base?
\(A\)
\(\ce{NaX + HCl \rightarrow NaCl + HX}\)
\(\ce{n(HCl)} = 0.100 \times 24.4 \times 10^{-3} = 2.44 \times 10^{-3}\ \text{mol}\)
\(\ce{n(NaX)}=2.44 \times 10^{-3}\ \text{mol in 20 mL sample.}\)
\(\ce{c(NaX)}=\dfrac{2.44 \times 10^{-3}}{20 \times 10^{-3}} =0.122\ \text{mol L}^{-1}\)
\(\ce{n(NaX)}=0.122 \times 0.1=0.0122\ \text{mol (in 100 mL sample)}\)
\(\ce{MM(NaX)}=\dfrac{1}{0.0122}=82\ \text{g mol}^{-1}\)
\(\Rightarrow A\)
A 25.0 mL sample of a 0.100 mol L\(^{-1}\) hydrochloric acid solution completely reacted with 23.4 mL of sodium hydroxide solution.
What volume of the same sodium hydroxide solution would be required to completely react with 25.0 mL of a 0.100 mol L\(^{-1}\) acetic acid solution?
\(B\)
→ The strength of the acid does not affect the volume of \(\ce{NaOH}\) required for nuetralisation.
→ It is dependent on stoichiometric ratios and both \(\ce{HCl}\) and \(\ce{CH3COOH}\) are monoprotic and so react in 1:1 ratio with sodium hydroxide.
\(\Rightarrow B\)