Question 1
10.618 g of an unknown salt is dissolved in a coffee cup calorimeter that contains 50.0 mL of water. The measured temperature decreased from 23.8 °C to 22.7 °C. Identify the unknown salt. The specific heat of water is 4.184 J g
-1 °C
-1, and assume the density of the solution is 1.00 g mL
-1.
◦ NaNO
3, D
rH = 20.50 kJ mol
-1◦ NaBr, D
rH = -0.60 kJ mol
-1◦ NaF, D
rH = 0.91 kJ mol
-1◦ LiBr∙2H
2O, D
rH = -23.26 kJ mol
-1◦ LiNO
3, D
rH = -2.51 kJ mol
-1Question 2
9.26 g of an unknown solid is dissolved in a coffee cup calorimeter that contains 62.0 mL of water. The measured temperature increased from 23.4 °C to 24.7 °C. The specific heat of water is 4.184 J g
-1 °C
-1, and assume the density of the solution is 1.00 g mL
-1. Calculate the molecular weight of the unknown solid if the D
rH was determined to be -2.51 kJ mol
-1 via another experiment.
◦ 48 g mol
-1◦ 69 g mol
-1◦ 93 g mol
-1◦ 184 g mol
-1◦ 76 g mol
-1
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