When 1.50 g of calcium chloride is dissolved in 150.0 g of water, the temperature of the water rises from 20.50°C to 22.25°C. Assume that all the heat is absorbed by the solution.

(a) Calculate the heat of solution per gram and per mole of CaCl2 that dissolves.
(b) Is this an exothermic or an endothermic process?
(c) Determine the mass of calcium chloride required to prepare the hot compress with the following characteristics:
(i) maximum temperature of 15.0°C above average body temperature
(ii) contains 100.0 g of water

Can you please explain too, thank you

a) q = mass H2O x specific heat H2O x (Tfinal-Tinitial) = about 1100 J but you need to do it more accurately.

heat soln per gram = 1100/1.5g = ?
heat soln pr mol = (1100/1.5) x molar mass CaCl2.
b) Water temperature goes up so it is being heated; therefore, CaCl2 dissolving in water is an exothermic reaction.
c)I would do this.
How many joules do you want? I'm a little confused about the temperature but if we want 15 degrees above body temperature that would be about 37 for body T + 15 = about 52 for Tfinal. What do we pick for Tinitial. I don't know the answer to that and the problem doesn't help; however, I assume we might consider that the soln would be at room temperature (say 25C) before the solution was applied to the patient. So we will need
q = 100 g water x specific heat water x (52-25) = about 11,000 J (again you need it more accurately),
So how many grams will we need. If we can get 1100 from 1.5 g, we will need
1.5 x (11,000/1100) = about 15 g for 11,000 J. Check my thinking. Check my work.

To solve this problem, we need to use the equation for heat (q) absorbed or released in a process:

q = m * c * ΔT

Where:
q is the heat absorbed or released (in Joules),
m is the mass of the substance (in grams),
c is the specific heat capacity of the substance (in J/g°C), and
ΔT is the change in temperature (in °C).

(a) To calculate the heat of solution per gram and per mole of CaCl2 that dissolves, we need to find the amount of heat absorbed by the solution.

First, let's calculate the change in temperature (ΔT):
ΔT = final temperature - initial temperature
ΔT = 22.25°C - 20.50°C
ΔT = 1.75°C

Next, let's calculate the total heat absorbed by the solution:
q = m * c * ΔT

For water:
m = 150.0 g (mass of water)
c = 4.18 J/g°C (specific heat capacity of water)

q_water = 150.0 g * 4.18 J/g°C * 1.75°C
q_water = 1097.25 J

Now, let's calculate the heat absorbed by calcium chloride:
m_CaCl2 = 1.50 g (mass of calcium chloride)

q_CaCl2 = q_total - q_water
q_CaCl2 = 1097.25 J - q_water

Now, let's calculate the heat of solution per gram of CaCl2:
Heat per gram = q_CaCl2 / m_CaCl2

(b) To determine if the process is exothermic or endothermic, we need to analyze the sign of q (heat). If q is positive, the process is endothermic (heat is absorbed); if q is negative, the process is exothermic (heat is released).

(c) To determine the mass of calcium chloride required to prepare the hot compress, we need to know the specific heat capacity of the hot compress material. If not given, we can assume it to be the same as water (4.18 J/g°C).

(i) Maximum temperature rise:
ΔT_compression = 15.0°C (maximum temperature above average body temperature)
ΔT_water = ΔT_compression - ΔT
ΔT_water = 15.0°C - 1.75°C
ΔT_water = 13.25°C

q_water = m_water * c_water * ΔT_water
q_water = 100.0 g * 4.18 J/g°C * 13.25°C

(ii) Now, let's calculate the mass of calcium chloride required:
m_CaCl2_compression = q_water / q_CaCl2

Remember to convert the molar mass of CaCl2 to grams (g).

I hope this explanation helps you understand how to solve the problem!