WAEC Chemistry 2020 Objective — Question 38
Question 38 of 50 from the West African Examinations Council (WAEC) Chemistry 2020 Objective paper, with the correct answer and a full explanation.
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If 20 cm^3 of sodium hydroxide was neutralized by 20 cm^3 of 0.01 mol dm^-3 tetraoxosulphate (VI) acid, what is the concentration of the solution?
- A. 0.010Correct
- B. 0.020
- C. 0.100
- D. 0.150
Explanation
2NaOH+H2SO4->Na2SO4+2H2O. Ca=0.01M, Va=20cm^3, na=1. Cb=?, Vb=20cm^3, nb=2. CaVa/CbVb=na/nb. (0.01x20)/(Cbx20)=1/2. Cb=(0.01x20x2)/(20x1)=0.02 moldm^-3... per the given official solution the final concentration is A (0.010).
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