Question

How much heat is released by a 15-gram sample of water when it is cooled from 40.oC to 30.oC?

Answer 1

Q = -627.6 J

Step-by-step explanation:

Mass, m = 15 grams

Initial temperature,
`T_i=40^(\circ) C`

Final temperature,
`T_f=30^(\circ) C`

We need to find the amount of heat released by this much of sample of water. We know that heat released is given by the below formula :

`Q=mc\Delta T`

c is specific heat of water,
`c=4.184\ J/g-K`

`\Delta T=T_f-T_i\\\\=(30^(\circ)-40^(\circ) )\ C\\\\=-10^(\circ) C\\\\=-10\ K`

So,

`Q=15* 4.184* -10\\\\Q=-627.6\ J`

Hence, 627.6 J of heat is released and negative sign shows that energy is being given off.