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4 years ago

How many kilojoules are released when 8.2 g of water condenses at 100 °c and cools to 15 °c?

Chemistry

1 answer:

MrRa [10]4 years ago

3 0

Answer:- 2.92 kJ of heat is released.

Solution:- We have water at 100 degree C and it's going to be cool to 15 degree C.

So, change in temperature, $\Delta T$ = 15 - 100 = -85 degree C

mass of water, m = 8.2 g

specific heat of water, c = $4.184\frac{J}{^0C.g}$

The equation used for solving this type of problems is:

$q=mc\Delta T$

Let's plug in the values in the equation and solve it for q which is the heat energy:

q = (8.2)(4.184)(-85)

q = -2916.248 J

They want answer in kJ. So, let's convert J to kJ and for this we divide by 1000.

$q=-2916.248J(\frac{1kJ}{1000J})$

q = -2.92 kJ

Negative sign indicates the heat is released. So, in the above process of coiling of water, 2.92 kJ of heat is released.

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See explanation

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3 years ago

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Be sure to answer all parts. Sulfur dioxide is released in the combustion of coal. Scrubbers use lime slurries of calcium hydrox

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Answer: The balanced chemical equation is written below and $\Delta S^o$ for the reaction is -160.6 J/K

Explanation:

When calcium hydroxide reacts with sulfur dioxide, it leads to the formation of calcium sulfate and water molecule.

The chemical equation for the reaction of calcium hydroxide and sulfur dioxide follows:

$Ca(OH)_2(s)+SO_2(g)\rightarrow CaSO_3(s)+H_2O(l)$

To calculate the entropy change of the reaction, we use the equation:

$\Delta S^o_{rxn}=\sum [n\times \Delta S^o_{products}]-\sum [n\times \Delta S^o_{reactants}]$

For the given reaction:

$\Delta S^o_{rxn}=[(1\times \Delta S^o_{CaSO_3(s)})+(1\times \Delta S^o_{H_2O(l)})]-[(1\times \Delta S^o_{Ca(OH)_2(s)})+(1\times \Delta S^o_{SO_2(g)})]$

Taking the standard entropy change values:

$\Delta S^o_{CaSO_3(s)}=101.4Jmol^{-1}K^{-1}\\\Delta S^o_{H_2O(l)}=69.9Jmol^{-1}K^{-1}\\\Delta S^o_{Ca(OH)_2(s)}=83.4Jmol^{-1}K^{-1}\\\Delta S^o_{SO_2(g)}=248.5Jmol^{-1}K^{-1}$

Putting values in above equation, we get:

$\Delta S^o_{rxn}=[(1\times (101.4))+(1\times (69.9))]-[(1\times (83.4))+(1\times (248.5))]\\\\\Delta S^o_{rxn}=-160.6J/K$

Hence, the balanced chemical equation is written above and $\Delta S^o$ for the reaction is -160.6 J/K

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3 years ago