Instant hot packs contain a solid and a pouch of water. When the pack is squeezed, the pouch breaks and the solid dis- solves, increasing the temperature because of the exothermic reaciton. The following reaction is used to make a hot pack: H2O LiCl1s2 ¡ Li 1aq2 + Cl 1aq2 ∆H = -36.9 kJ. What is the final temperature in a squeezed hot pack that contains 25.0 g of LiCl dissolved# in 125 mL of water? Assume a specific heat of 4.18 J>1g °C2 for the solution, an initial temperature of 25.0 °C, and no heat transfer between the hot pack and the environment.

Video transcript

Hi everyone. So we have a one kg block of nickel metal And it's headed to 98°C. That was dropped in a coffee cup calorie meter containing 350 g of water? At 25.8°C. The temperature inside the cup became 41.3°C. We were asked if the heat loss from the metal was all absorbed by the water. What would be the final temperature of the system? All that the amount of heat transferred is even to the mass of the solution. Talk to specific heat. The solution times the temperature change. They're gonna be looking at the heat of nettle equal to the mass of nickel. That's a specific heat, nickel. How's the temperature change for a mask? Love one kg And in one kg 1000 g. So this is 1000 g. And we're looking for the heat of the nickel and the specific key capacity of nickel 0.44 course jewels are grams times degrees Celsius. And for the temperature change 41. Grace Celsius minus 98 Very Celsius. We get negative 56.7 Grace Celsius. I'll be plugging advice to get the heat of nickel was 1000 g From 0. doors programs. Times degrees Celsius. I was gonna get 56.7 Celsius. The heat of the medical 25, 174 0.8 jaws. So now we need to find the final temperature of the solution. Have the heat of water to the mass of water specific heat capacity of the water. How's the temperature change for the heat of the water? 25174. I ate jaws, the mask, 350 grams for the specific heat capacity of the water. 4.184. Those programs, times degrees Celsius for the temperature change and the final temperature -25.8°C. Then I can plug in advice to find the final temperature. I have 25,000 174 0. doors. It was 350 grams £4.184. Our grams times degrees Celsius. The final temperature -25.8°C When I was 25,074. Eight jaws. Just 1464 point forward yours three degrees Celsius. That was the final temperature -25.8. MS Celsius Created by both sides by 1,464. What for those part degree Celsius at 17.19 cassius, It's the final temperature -25.8. Very Celsius, Hope you at 25.8 resale system. Both sides. For the final temperature. They get 43 C. Thanks for watching my video and I hope it was helpful