Skip to content

Course home

Sign up

Analysis

EasyMedium
123456789101112131415161718192021222324252627282930313233
Question 30

An agricultural scientist analysed the juice vesicles of a specific variety of lemon to determine the acidity of their central vacuoles. They obtained the following mean measurements for a single vacuole:

  • Mean volume of a vacuole: 2.5×10−5 cm32.5 \times 10^{-5}\text{ cm}^32.5×10−5 cm3
  • Mean quantity of H+\text{H}^+H+ ions per vacuole: 7.5×10−11 mol7.5 \times 10^{-11}\text{ mol}7.5×10−11 mol
a.

Calculate the mean H+\text{H}^+H+ ion concentration within a vacuole in this juice vesicle. Give your answer in mol dm−3\text{mol dm}^{-3}mol dm−3.

[2]
b.

The formula to calculate pH is:

pH=−log⁡10[H+] \text{pH} = -\log_{10} [\text{H}^+] pH=−log10​[H+]

where [H+][\text{H}^+][H+] is the hydrogen ion concentration in mol dm−3\text{mol dm}^{-3}mol dm−3. Use your calculation from part (a) to find the mean pH of the vacuoles. Give your answer to 2 significant figures.

[2]
Markscheme

Analysis Questions

  1. A Level
  2. /Biology
  3. /Analysis

45 exam-style questions on OCR A A Level Biology Analysis. Each one has a worked solution and a mark scheme showing where the marks go.

Question bank