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Calculate the amount of heat needed to boil 41.1 g of water (H2O), beginning from a temperature of 84.7 C . Be sure your answer has a unit symbol and the correct number of significant digits.

Sagot :

Explanation:

We need to go through to stages to boil 41.1 g of water. We have to heat the sample of water from 84.7 °C to 100 °C (the boiling point) And then we have to provide enough heat to boil all the sample of water.

a) Heating from 84.7 °C to 100 °C:

This is calculated using the formula:

Q₁ = m * C * ΔT

Where Q₁ is the amount of heat, m is the mass of the sample, C is the specific heat of water and ΔT is the temperature change. We already know these values:

m = 41.1 g

C = 4.184 J/(g*°C)

ΔT = Tfinal - Tinitial = 100 °C - 84.7 °C

ΔT = 15.3 °C

Replacing these values we can get the amount of heat necessary for the first step:

Q₁ = m * C * ΔT

Q₁ = 41.1 g * 4.184 J/(g°C) * 15.3 °C

Q₁ = 2631 J

b) Boiling 41.1 g of water:

To find the amount of heat that we need to provide to the sample of water to completely boil it we can use this formula:

Q₂ = m * Cv

Where Cv is the latent heat of vaporization.

Cv = 2256 J/g

Q₂ = m * Cv

Q₂ = 41.1 g * 2256 J/g

Q₂ = 92721 J

c) Total amount of heat:

Qtotal = Q₁ + Q₂

Qtotal = 2631 J + 92721 J

Qtotal = 95352 J = 95400 J

Qtotal = 95.4 kJ

Answer: The amount of heat needed to boil the sample of water is 95.4 kJ or 95400 J.