Joules required to heat/how much heat is released

In summary: So for the second problem, you would use q=ΔH*m, where ΔH is the latent heat of steam and m is the mass of steam being converted to liquid water.
  • #1
jacob95
4
0

Homework Statement



1.)How many joules are required to heat 250 grams of liquid water from 25 C to 100 C

2.)How much heat is released when 200 grams of steam condenses?

Homework Equations



q=m*(delta) t*c
q=(delta)H*m

The Attempt at a Solution



1.)q=250g*75°C*4.186joules ? = 74 487joules ?
74 487 joules = 18,758 cal?
2.)
 
Last edited:
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  • #2
jacob95 said:

Homework Statement



How many joules are required to heat 250 grams of liquid water from 25 C to 100 C

How much heat is released when 200 grams of steam condenses?

Homework Equations



q=m*(delta) t*c
q=(delta)H*m



The Attempt at a Solution



I don't know how to begin


For the first one, you have the formula

Q=mcΔT, so what is c for water ? You are given m and you can get ΔT (the change in temperature). So just plug in the numbers.

For the second one. What is the latent heat of water for this case of going from a gas to a liquid?
 
  • #3
so would it be

q=250g*75°C*4.186j=78487.5 joules?
or
q=250g*75°C*1

then I would have to convert it to calories

78 487 joules = 18 758 cal?
 
Last edited:
  • #4
yes?
 
  • #5
jacob95 said:
so would it be

q=250g*75°C*4.186j=78487.5 joules?
or
q=250g*75°C*1

then I would have to convert it to calories

78 487 joules = 18 758 cal?

It would be the first one since c= 4.186 J/g°C
 
  • #6
thanks

what does ΔH stand for in

q=ΔH*m?
 
  • #7
jacob95 said:
what does ΔH stand for in

q=ΔH*m?

I think that's the latent heat.
 

Related to Joules required to heat/how much heat is released

1. How do you calculate the amount of heat released in a chemical reaction?

The amount of heat released in a chemical reaction can be calculated using the formula Q = m × c × ΔT, where Q is the heat released, m is the mass of the substance, c is the specific heat capacity, and ΔT is the change in temperature. This formula is known as the heat capacity equation.

2. What is the difference between joules required to heat and joules released?

Joules required to heat refers to the amount of energy needed to increase the temperature of a substance, while joules released refers to the amount of energy released or given off by a substance during a reaction or change in temperature. The former is an input of energy, while the latter is an output of energy.

3. How does the specific heat capacity of a substance affect the joules required to heat it?

The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 gram of that substance by 1 degree Celsius. Therefore, the higher the specific heat capacity, the more energy is needed to heat the substance, and the lower the specific heat capacity, the less energy is needed.

4. Can the joules required to heat a substance be negative?

No, the joules required to heat a substance cannot be negative. This is because heat is always transferred from a higher temperature to a lower temperature, resulting in a positive value for the amount of energy required.

5. How does the type of reaction affect the amount of heat released?

The type of reaction can greatly affect the amount of heat released. Exothermic reactions release heat, while endothermic reactions absorb heat. The amount of heat released or absorbed is dependent on the specific reactants and products involved in the reaction.

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