When 2.714 g of ax (s) dissolves in 127.4 g of water in a coffee-cup calorimeter the temperature rises from 23.3 °c to 37.1 °c. calculate the enthalpy change (in kj/mol) for the solution process. ax(s) → a+(aq) + x-(aq) assumptions for this calculation: the specific heat of the solution is the same as that of pure water (4.18 j/gk) the density of water = 1.000 g/ml the liquid’s final volume is not changed by adding the solid the calorimeter loses only a negligible quantity of heat. the formula weight of ax = 59.1097 g/mol. be sure you include the correct sign for the enthalpy change.

Answer : The enthalpy change for the solution is 166.34 kJ/mol

Explanation :

First we have to calculate the enthalpy change of the reaction.

Formula used :

where,

= change in enthalpy = ?

C = heat capacity of water =

m = total mass of sample = 2.174 + 127.4 = 129.6 g

= initial temperature =

= final temperature =

Now put all the given values in the above expression, we get:

Now we have to calculate the moles of AX added to water.

Now we have to calculate the enthalpy change for the solution.

As, 0.04592 moles releases heat = 7638.36 J

So, 1 moles releases heat =

Therefore, the enthalpy change for the solution is 166.34 kJ/mol

When 2.714 g of AX(s) dissolves in 127.4 g of water in a coffee-cup calorimeter and the temperature rises from 23.3 °C to 37.1 °C, the enthalpy change for the solution process is -163 kJ/mol.

A coffee cup calorimeter is a constant-pressure calorimeter. As such, the heat that is measured in such a device is equivalent to the change in enthalpy.

A solution is prepared by dissolving 2.714 g of AX (solute) in 127.4 g of water (solvent). The mass of the solution (m) is:

When AX is dissolved, the temperature of the system rises from 23.3 °C to 37.1 °C. Assuming the solution has the same specific heat as water (c = 4.18 J/g.K = 4.18 J/g.°C), we can calculate the heat absorbed by the calorimeter using the following expression.

According to the law of conservation of energy, the sum of the heat absorbed by the calorimeter (Qcal) and the heat released by the solution (Qsol) is zero.

2.714 g of AX(s) with a molar mass of 59.1097 g/mol are dissolved. The corresponding moles are:

Finally, we can calculate the enthalpy change (in kJ/mol) for the solution process using the following expression.

When 2.714 g of AX(s) dissolves in 127.4 g of water in a coffee-cup calorimeter and the temperature rises from 23.3 °C to 37.1 °C, the enthalpy change for the solution process is -163 kJ/mol.

You can learn more about calorimetry here:

n has four pairs of electrons in the valence shell, electrons repel one another ,n has 7 protons in its nucleus, and since n has 7 protons, it must fill the second shell, giving it 4 pairs of electrons. the electrons form 3 bonds and 1 lone pair of electrons. each pair of electrons repels the other pairs, so they are equally far apart.

so all of the above