Question

A 5.80 g sample of solid NH4Br (s) is dissolved in 117 mL of water in a coffee cup calorimeter. Once all of the NH4Br (s) is dissolved in the water, the final temperature of the solution is found to be 6.73°C. If the initial temperature of the water in the calorimeter was 21.63 °C, calculate the calorimeter constant (in J/K) for the coffee cup calorimeter. Report your answer to three significant figures. The heat of solvation of NH4Br (s) is 16.78 kJ/mol.

Answer #1

Assuming system to be adiabatic, the heat evolved due to dissolution of NH4Br will be absrobed by the caloriemter and solution

The heat of solvation of NH4Br = 16.78 KJ / moles ( so this endothermic reaction)

The solution will require this much of energy dissolve

The moles of NH4Br dissolved = Mass / Molecular weight = 5.8 g / 98 = 0.0591

so heat absorbed (used) = 16.78 KJ X 0.0591 = 0.991KJ = 991 J

Heat lost =

= mass of water X specific heat X change in temperature + calorimeter constant X change in temperature

= 7286.9 + calorimeter constant X 14.9

Heat gained by solution = 991 Joules

calorimeter constant = 422.54 J / K

A 3.56 g sample of solid
NH4C2H3O2 (s) is
dissolved in 418 mL of water in a coffee cup calorimeter. Once all
of the NH4C2H3O2 (s) is
dissolved in the water, the final temperature of the solution is
found to be 24.81°C. If the initial temperature of the water in the
calorimeter was 20.81 °C, calculate the calorimeter constant (in
J/K) for the coffee cup calorimeter.
Report your answer to three significant figures.
The heat of solvation of
NH4C2H3O2 (s)...

A 3.98 g sample of solid NaBr (s) is dissolved in 361 mL of
water in a coffee cup calorimeter. Once all of the NaBr (s) is
dissolved in the water, the final temperature of the solution is
found to be 30.04°C. If the initial temperature of the water in the
calorimeter was 21.84 °C, calculate the calorimeter constant (in
J/K) for the coffee cup calorimeter.
The heat of solvation of NaBr (s) is -0.60 kJ/mol.

A student determines the heat of dissolution of solid
ammonium bromide using a coffee-cup calorimeter of
negligible heat capacity.
When 6.34 g of
NH4Br(s) is dissolved in
119.00 g of water, the temperature of the solution
drops from 25.00 to 22.76 °C.
Based on the student's observation, calculate the enthalpy of
dissolution of NH4Br(s) in kJ/mol.
Assume the specific heat of the solution is 4.184 J/g°C.
ΔHdissolution = kJ/mol

When a 5.93-g sample of solid sodium hydroxide dissolves in 39.8
g of water in a coffee-cup calorimeter (see above figure) the
temperature rises from 22.00 oC to 56.12 oC. Calculate H in kJ/mol
NaOH for the solution process. NaOH(s) Na+(aq) + OH-(aq) The
specific heat of water is 4.18 J/g-K.

When a 3.81-g sample of solid ammonium chloride dissolves in
57.9 g of water in a coffee-cup calorimeter (see above figure) the
temperature falls from 24.00 oC to 19.94 oC. Calculate H in kJ/mol
NH4Cl for the solution process. NH4Cl(s) NH4+(aq) + Cl-(aq) The
specific heat of water is 4.18 J/g-K.

When 4.93 g of ammonium bromide (NH4Br) is dissolved in 103 g of
water in a styrofoam calorimeter of negligible heat capacity, the
temperature drops from 25.00 to 22.97 °C. Based on this
observation, calculate q for the water and ΔH° for the process,
assuming that the heat absorbed by the salt is negligible.
NH4Br(s) NH4+(aq) + Br- (aq)
The specific heat of water is 4.184 J °C-1 g-1.

A 9.07-g sample of NaOH is dissolved in 104.9 g of water in a
coffee cup calorimeter. The temperature of the solution rises from
15.49°C to 23.76°C. Calculate ∆Hrxn,
in kJ for the dissociation of NaOH in water Assume that the heat
capacity for the solution is 4.18 J/g°C.

1.
When a solid dissolves in water, heat may be evolved or
absorbed. The heat of dissolution
(dissolving) can be determined using a coffee cup
calorimeter.
In the laboratory a general chemistry student finds that when
6.20 g of CsClO4(s)
are dissolved in 115.60 g of water, the
temperature of the solution drops from
22.87 to 19.50 °C.
Based on the student's observation, calculate the enthalpy of
dissolution of CsClO4(s) in
kJ/mol.
Assume the specific heat of the solution is...

Using the following thermal chemical data (use Hess’s law)
2Fe(s) + 6HF(g) —> 2FeF3(s) + 3H2(g)
?rH•= -1787.4 kJ/mol
2Fe(s) + 6HCl(g) —> 2FeCl3(s) + 3H2(g)
?rH•= -1457.0 kJ/mol
calculate?rH• for the following reaction:
FeCl3(s) + 3HF(g) —> FeF3(s) + 3HCl(g)
2. when 19.86g NaOH is dissolved in 125 mL of water in the
coffee-cup calorimeter, the temperature rises from 23•C to 65•C.
what is the enthalpy change per mole of the hydroxide dissolved in
the water? Assume that...

When a solid dissolves in water, heat may be evolved or
absorbed. The heat of dissolution
(dissolving) can be determined using a coffee cup
calorimeter.
In the laboratory a general chemistry student finds that when
18.53 g of
Cs2SO4(s) are dissolved in
100.40 g of water, the temperature of the solution
drops from 25.54 to
22.92 °C.
The heat capacity of the calorimeter (sometimes referred to as the
calorimeter constant) was determined in a separate
experiment to be 1.85 J/°C....

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