Question

The graph below shows how solubility changes with temperature.

A graph with the horizontal axis showing temperature ranging from 0 to 10 in units of 10 and the vertical axis solubility in grams of salt per 100 grams of water. Several compounds are shown. All data are approximate. The substances and their coordinates are as follows: upper N a upper C l: 0, 38; 10, 38; 20, 38; 30, 38; 40, 39; 50, 39; 60, 39; 70, 40; 80, 40; 90, 40; 100, 40. Upper N a subscript 2 upper H upper A s upper O subscript 4: 0, 5; 10, 18; 20, 28; 30, 39; 40, 49; 60, 65; 80, 82. Upper B a (upper N upper O subscript 3) subscript 2: 0, 5; 10, 8; 30, 12; 40, 15; 50, 18; 60, 20; 80, 28; 100, 33. Upper N a subscript 2 upper S upper O subscript 4: 0, 5; 5, 8; 10, 10; 15, 15; 20, 20; 25, 20; 28, 35; 30, 40; 32, 49; 33, 50; 35, 50; 40, 48; 50, 47; 60, 46; 70, 45; 80, 43; 90, 32; 100, 40. Upper C 3 subscript 2 (upper S upper O subscript 4) subscript 3 dot 9 upper H subscript 2 upper O: 0, 18; 20, 10; 30, 8; 50, 5; 60, 3; 80, 1; 100, 0.

Which two solutions have similar solubilities at 40°C?
Na2SO4 and NaCl
Na2HAsO4 and NaCl
Na2HAsO4 and Na2SO4
Ba(NO3)2 and Ce2(SO4)3 • 9H2O

Answer 1

Na2HAsO4 and Na2SO4 — both have solubilities of about 48–49 g per 100 g water at 40°C (nearly identical on the graph).