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Question

0.700 moles of an unknown solid is placed into water to make 150.0 mL of solution. The solutions temperature decreases by 6.21 Celsius calculate heat change for the dissolution of the unknown solid.( The specific heat of the solution Is 4.18 J/ g Celsius and the density of the solution is 1.02 g/mL

Answer 1

q = mC∆T

q = heat = ?

m = mass = 150.0 ml x 1.02 g/ml = 153 g

C = specific heat = 4.18 J/gº

∆T = change in temperature = -6.21º

Solving for q..

q = (153 g)(4.18 J/gº)(6.21º)

q = 3972 J = 3970 J (3 sig. figs.) The sign is + because the temperature of solution decreased meaning the reaction is endothermic and thus q is positive.