Question

initial temp of solution in C	21.2	21.2	21.2
final temp of solution in C	36.4	35.2	38.7
change in temp in C	15.2	14.0	17.5
Determine Mass of solution:	X	X	X
weight of test tube with solution in g	112.24	109.57	179.48
weight of empty test tube with cap in g	63.15	63.15	63.15
mass of solution in g	49.09	46.42	116.33
Amount of heat released (J) the specific heat capacity of the solution is 5.49 J/(K x g)	?	?	?
moles of NaC2H3O2(3H2O) in test tube (mol) There is 52.1g of this solution in each tube. Molar mass of this equation is 136.1g/mol	?	?	?
Enthaply of phase change (kJ/mol) for NaC2H3O2(3H2O)	?	?	?

Amount of heat released (J) calculations:

Calculate the average enthaply of phase change:    ________ kJ/mol

When doing these calculations change the mass of the solution to 52.08g.

Answer 1

Trial 1

Heat released = 49.09 * 5.49 * 15.2 = 4096.46 J = 4.096 kJ

moles of NaC2H3O2(3H2O) in test tube (mol) = 52.1/136.1

= 0.3828 mol

Enthalpy change = 4.096/0.3828 = 10.7 kJ/mol

Trial 2

Heat released = 46.42 * 5.49 * 14 = 3567.84 J = 3.568 kJ

moles of NaC2H3O2(3H2O) in test tube (mol) = 52.1/136.1

= 0.3828 mol

Enthalpy change = 3.568/0.3828 = 9.32 kJ/mol

Trial 3

Heat released = 116.33 * 5.49 * 17.5 = 11176.4 J = 11.176kJ

moles of NaC2H3O2(3H2O) in test tube (mol) = 52.1/136.1

= 0.3828 mol

Enthalpy change = 11.176/0.3828 = 29.2 kJ/mol

Average enthalpy of change = 10.7+9.32+29.2/3

= 16.4 kJ/mol