Question

How many kj of heat are needed to completely melt 32.3 g of h2o, given that the water is at its melting point? the heat of fusion for water is 6.02 kj/mole. how many kj of heat are needed to completely melt 32.3 g of h2o, given that the water is at its melting point? the heat of fusion for water is 6.02 kj/mole. 1.79 3.35 0.557 10.8 none of the above?

Answer 1

Answer: fourth option, 10.8 kJ

Explanation:

The heat of fusion, also named latent heat of fusion, is the amount of heat energy required to change the state of a substance from solid to liquid (at constant pressure).

The data of the heat of fusions of the substances are reported in tables and they can be shown either per mole or per gram of substance.

In this case we have that the heat of fusion for water is reported per mole: 6.02 kJ/mole.

The formula to calculate how many kJ of heat (total heat) are needed to completely melt 32.3 g of water, given that the water is at its melting point is:

• Heat = number of moles × heat of fusion

The calculations are:

• number of moles = mass / molar mass

        number of moles = 32.3 g / 18.015 g/mol = 1.79 mol

       

• Heat = 1.79 mol × 6.02 kJ / mol = 10.8 kJ ← answer

Answer 2

The amount of heat required to completely melt 32.3 g water is $\boxed{{\text{10}}{\text{.78 kJ}}}$

Further explanation:

Latent heat:

The heat released or absorbed during the process of conversion of the physical state of a substance without altering the temperature is known as the latent heat.

When the physical state changes from the solid phase to liquid phase then the amount of heat absorbed in this process to completely convert the solid into liquid without altering the temperature is known as the latent heat fusion.

The formula to calculate heat absorbed from the latent heat of fusion is,

${\text{q}}={\text{n}}{{\text{H}}_{\text{f}}}$                                  …… (1)

Here,

q is heat absorbed.

n denotes the number of moles of substance.

${{\text{H}}_{\text{f}}}$is latent heat of fusion.

The formula to calculate the moles of water is as follows:

${\text{Moles of water}}=\frac{{{\text{Given mass of water}}}}{{{\text{Molar mass of water}}}}$                …… (2)

The mass of the given water is 32.3 g.

The molar mass of water is 18.015 g/mol.

Substitute these values in equation (2).

$\begin{gathered}{\text{Moles of water}}=\left({{\text{32}}{\text{.3 g}}}\right)\left({\frac{{{\text{1 mol}}}}{{{\text{18}}{\text{.015 g}}}}}\right)\\={\text{1}}{\text{.792950 mol}}\\\approx{\text{1}}{\text{.79 mol}}\\\end{gathered}$

The moles of water is 1.79 mol.

The latent heat of fusion is 6.02 kJ/mol.

Substitute these values in equation (1).

$\begin{gathered}{\text{q}}=\left({{\text{1}}{\text{.79 mol}}}\right)\left({\frac{{{\text{6}}{\text{.02}}\;{\text{kJ}}}}{{{\text{1 mol}}}}}\right)\\=10.7758{\text{ kJ}}\\\approx{\text{10}}{\text{.78 kJ}}\\\end{gathered}$

So 10.78 kJ is needed to completely melt 32.3 g of water.

Learn more:

1. The difference between heat and temperature.:brainly.com/question/914750

2. Determine the process by which water enters into the atmosphere?: brainly.com/question/2037060

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Thermodynamics

Keywords: latent heat, latent heat of fusion, q, Hf, 10.78 kJ, 32.3 g, water, moles of water, molar mass of water, 18.015 g/mol, melt, 6.02 kJ/mol.