page 13 22. Consider the reaction pathway below. W Z Y X ∆H = −210 kJ mol−1 ∆H = −50 kJ mol−1 ∆H = −86 kJ mol−1 According to Hess’ law, the ∆H value, in kJ mol−1, for reaction Z to Y is: A −74 B +74 C −346 D +346 23. 50.0 cm3 of 0.100 mol l−1 ammonia solution was transferred to a 250 cm3 volumetric flask. The flask was made up to the mark with deionised water. The final concentration, in mol l−1, of the ammonia solution is: A 2.0 × 10−2 B 2.5 × 10−2 C 4.0 × 10−2 D 5.0 × 10−2 24. An experiment involves reacting 0.02 moles of silver ions with ions of a group 7 element to form 2.868 g of precipitate. Which of the following is the precipitate? A Silver(I) fluoride B Silver(I) chloride C Silver(I) bromide D Silver(I) iodide [Turn over