I'm going to have to say A. My reason to that is because when you leave a cup of hot cocoa (assuming its hot), it gives off the heat (exothermic) the
Divide the mass of the compound in grams by the molar mass you just calculated. The answer is the number of moles of that mass of compound. For example, 25 grams of water equals 25/18.016 or 1.39 moles.
48.3 g AgNO3 / 169.9 g/mol = 0.284 moles AgNO3
0.284 mol AgNO3 X (1 mol Ag2CrO4/2 mol AgNO3) = 0.142 mol Ag2CrO4
0.142 mol Ag2CrO4 X 331.7 g/mol = 47.1 g Ag2CrO4