Calculating Heat Released During Water Freezing

In summary, the amount of heat emitted when 12.4 g of water freezes to solid air is -4.14 kJ. This is determined by using the heat of fusion and the molar mass of water to calculate the heat change, which is negative because freezing is an exothermic process. However, it is important to pay attention to the language of the question, as it may ask for the negative value of the heat change, which in this case would be 4.14 kJ.
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Homework Statement


Calculate the amount of heat emitted when 12.4 g of water freezes to solid air.

Homework Equations


heat of fusion = 6.02 KJ
1 mol H2O = 18.02 g H2O

The Attempt at a Solution


12.4 g H2O x 1 mol H2O/ 18.02 g H2O x (-6.02 KJ) / 1 mol H2O = - 4.14 kJ

I am unsure whether the answer is positive or negative.
The answer in the book is positive 4.14 kJ, but freezing is exothermic ( releasing energy).
 
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You have to pay attention to the language. The question asks for "the amount of heat emitted", which will be minus the heat change of the water, that latter being what you calculated.
 
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1. What is the formula for calculating heat released during water freezing?

The formula for calculating heat released during water freezing is Q = m * L, where Q is the heat released in Joules, m is the mass of water in grams, and L is the latent heat of fusion for water, which is 334 Joules/gram.

2. How do you determine the mass of water for this calculation?

The mass of water can be determined by measuring the amount of water in grams using a scale or by converting the volume of water in milliliters to grams using the density of water, which is 1 gram/mL.

3. How do you find the latent heat of fusion for water?

The latent heat of fusion for water can be found in a reference table or by doing a quick internet search. It is a constant value of 334 Joules/gram.

4. Is the heat released always the same for every quantity of water?

Yes, the heat released during water freezing is always the same for every quantity of water. This is because the latent heat of fusion for water is a constant value.

5. Can this formula be used for other substances besides water?

No, this formula is specific to water and cannot be used for other substances. Each substance has its own latent heat of fusion, which would need to be used in the calculation.

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