Question

A sample of 2.21 grams of Z is dissolved into 500 grams of water which is in a styrofoam coffee cup. The temperature is monitored and is found to drop from 23.512°C to 23.269°C. What is ΔHsolution for substance Z? Assume no heat is lost/gained by the cup itself. The specific heat of water is 4.184 J/g·°C and the molecular weight of Z is 148 g/mol.

A. -50.25 kJ/mol of Z
B. -25.00 kJ/mol of Z
C. -13.40 kJ/mol of Z
D. -7.20 kJ/mol of Z

Answer 1

To calculate ΔHsolution for substance Z, we can use the equation: ΔHsolution = ΔT * (mass of water * specific heat of water). First, calculate the change in temperature (ΔT) by subtracting the final temperature from the initial temperature. Then, plug in the values into the equation to calculate ΔHsolution. The answer is not among the choices provided, but the closest option is A. -50.25 kJ/mol of Z.

Step-by-step explanation:

The change in temperature of the water in the coffee cup can be used to calculate the ΔHsolution for substance Z.

To calculate ΔHsolution, we can use the equation:

ΔHsolution = ΔT * (mass of water * specific heat of water)

First, calculate the change in temperature (ΔT) by subtracting the final temperature from the initial temperature: ΔT = 23.269°C - 23.512°C = -0.243°C

Next, plug in the values into the equation:

ΔHsolution = -0.243°C * (500g * 4.184 J/g·°C)

Simplifying the equation, we get:

ΔHsolution = -0.243°C * 2092 J/°C = -503.956 J

Finally, convert the result to kJ/mol by dividing by the molar mass of Z: -503.956 J / 0.00221 kg/mol = -228155.65 J/mol = -228.16 kJ/mol.

Therefore, the value of ΔHsolution for substance Z is -228.16 kJ/mol. The answer is not listed among the choices provided, but the closest option is A. -50.25 kJ/mol of Z.