Hi! I was a bit confused about how to input the information and solve these two questions. By the way, the first question is split into two parts because it is continued on the next page of the book. The questions are 65 and 66. I still couldn't figure them out after looking at the answer key for them, and I was still confused about how they solved them.   

Hope the images are clear enough!

65 -In this question we will use q= mc Δt
M= mass of solution = CaCl₂ + water
We need to know final temperature of the solution.
First calculate q = n ΔH
Here n is the number of moles of CaCl₂ and ΔH is the dissolution (given) of CaCl₂ .

67
In this question also we will use q= mc Δt
M= mass of solution = total of 100+300 = 400g (given)
We need to know final temperature of the solution.
First calculate q = n ΔH
Here n is the number of moles of water formed and ΔH is the reaction enthalpy.
Molarity and volume of HCl are given so calculate moles of HCl. Similarly calculate moles of Ba(OH)2 and check which one is the Limiting reactant .From LR calculate moles of water formed and then calculate q and then final temperature.

ohh ok thank you!

For question 65, I got 39.2 degrees Celsius; for 66, I got 26.8 degrees Celsius.

Both of your answers are correct

yayy! 

thank you