Question

1)350.0 g of H₂O at 30.0 ^oC is heated to 85.0 ^oC.
How many kJ of heat did it gain from the environment?
The specific heat, c, of water is 4.184 J/g·C .  

2)A sample of a metal at 90.00°C was added to 200.0 g H ₂O at 21.00°C. The temperature rose to 24.50°C. [Specific heat of H ₂O is 4.184 J/(g °C). Specific heat of the metal is 0.949 J/(g°C). How many grams of metal was it?\

3)Use the information in this thermochemical equation to solve the following problem.   
AgNO₃   +   HCl   -> AgCl + HNO₃     
75.0 mL of 0.840 M AgNO₃ and 75.0 mL of 0.840 M HCl are mixed in a constant-pressure (coffee-cup) calorimeter.   The two solutions are both initially at 20.00 degree centigrade. Final temperature of combined solution is 26.80 ^oC. Assume that the aqueous solutions have the same specific heat as water (4.184 J/ g ^oC ) and the same density of water (1.00 g/mL) .
  
How much heat did the reaction release?
  
Hint: no limiting reagent, substances are presented in correct molar ratios.

Answer 1

1)
Given:
m = 350 g
C = 4.184 J/g.oC
Ti = 30 oC
Tf = 85 oC
use:
Q = m*C*(Tf-Ti)
Q = 350.0*4.184*(85.0-30.0)
Q = 8.05*10^4 J
Q = 80.5 KJ
Answer: 80.5 KJ

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