the specfic heat of water is 4.2 joules/g C. if you wish to heat 300 grams of water from 30C to 100C?

Question

how much heat is required?
please give formula

Answer 1

Heat = m * Cp * DeltaT.

Plug the numbers and get the answer. Watch the units!

However, because you are at 100 C, which is the boiling point of water, you may have to add the heat of vaporization to the result of the equation.

Take this number from the table in your book.

Answer 2

Yes when dealing with grams you use the kinetic formula of heat:

Ek=mc(Tf-Ti) where c=specific heat capacity of the compound

Ek=(300g)(4.2J/gC)(100C-30C)
=88200J
or 88.2KJ

Significant digits gives 8.8*10^4J or 8.8*10^1KJ

J=joules and Kj=kilo joules 1000J=1kJ

*This formula should be used only in case where there is a temperature change
------------------------------------------------------------------------------------ This is what you would do for this particular type of question now say they gave you only moles of water or grams and there was no temperature change, then potential energy formula of heat must be used.

Ep=nH

where n=moles and H=KJ/mol(heat capacity without temperature change)

Answer 3

The specific heat times the mass times the change in temperature