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Acids and bases (A-level only)

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Question 45

Calcium hydroxide is sparingly soluble in water, but reacts completely with dilute nitric acid.

Ca(OH)2(s)+2HNO3(aq)→Ca(NO3)2(aq)+2H2O(l) \text{Ca(OH)}_2(\text{s}) + 2\text{HNO}_3(\text{aq}) \rightarrow \text{Ca(NO}_3)_2(\text{aq}) + 2\text{H}_2\text{O}(\text{l}) Ca(OH)2​(s)+2HNO3​(aq)→Ca(NO3​)2​(aq)+2H2​O(l)

A chemist adds 250 cm3250\text{ cm}^3250 cm3 of 0.0800 mol dm−30.0800\text{ mol dm}^{-3}0.0800 mol dm−3 nitric acid to 1.20 g1.20\text{ g}1.20 g of solid calcium hydroxide.

a.

Show, by calculation, that the calcium hydroxide is in excess.

[4]
b.

The final mixture contains a saturated solution of Ca(OH)2\text{Ca(OH)}_2Ca(OH)2​ at 310 K310\text{ K}310 K.

At 310 K310\text{ K}310 K:

  • the solubility of Ca(OH)2\text{Ca(OH)}_2Ca(OH)2​ in this solution is 0.926 g dm−30.926\text{ g dm}^{-3}0.926 g dm−3
  • Kw=2.40×10−14 mol2 dm−6K_w = 2.40 \times 10^{-14}\text{ mol}^2\text{ dm}^{-6}Kw​=2.40×10−14 mol2 dm−6

Calculate the pH of this solution at 310 K310\text{ K}310 K. Give your answer to two decimal places. (Assume the molar mass of Ca(OH)2\text{Ca(OH)}_2Ca(OH)2​ is 74.1 g mol−174.1\text{ g mol}^{-1}74.1 g mol−1.)

[4]

Acids and bases (A-level only) Questions

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  3. /Acids and bases (A-level only)