1. A 100. mL solution of 0.35 mol of Ca 2+ (aq) was mixed with 0.50 mol of F - (
ID: 499773 • Letter: 1
Question
1. A 100. mL solution of 0.35 mol of Ca2+ (aq) was mixed with 0.50 mol of F-(aq) ions, and CaF2 was percipitated:
The temperature of the solution increased by 10.5 Celcius. What was the enthalpy change for the chemical reaction? What was the enthalpy change for the production of 1 mol of CaF2? Assume that the solution has the same density and the specific heat of water.
2. to warm 400.0g of water, 0.050 mol of ethanol (C2H5OH) is burned. The water warms from 24.6 Celcius to 65.5 Celcius. What is the heat of the reaction, and what is he Enthalpy change of the reaction on molar basis?
Explanation / Answer
1)
total mass of solution = 100 g
specific heat = 4.184 J / goC
temperature rise = 10.5 oC
Q = m Cp dT
= 100 x 4.184 x 10.5
= 4393.2 J
Ca+2 + 2F- ----------------> CaF2
1 2
0.35 0.50
here limitng reagent is F-.
Enthalpy = - Q / n
= - 4393.2 x 10^-3 / 0.5
Enthalpy = - 8.79 kJ/mol
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