Joules required to heat/how much heat is released

[jacob95]

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.)

 

[rock.freak667]

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?

 

[jacob95]

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?

 

[jacob95]

yes?

 

[rock.freak667]

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

 

[jacob95]

thanks

what does ΔH stand for in

q=ΔH*m?

 

[nayfie]

what does ΔH stand for in

q=ΔH*m?

I think that's the latent heat.