A dilute aqueous solution of calcium hydroxide at 25 degree C reacts with gaseou

Question

A dilute aqueous solution of calcium hydroxide at 25 degree C reacts with gaseous hydrogen chloride via the following reaction. If the hydrogen chloride enters the reactor at 88.0 degree C, and the solution exits at 25 degree C, how much heat must be removed for every mole of CaCl2 produced? The heat of solution of Ca(OH)2 is -1008.2 kJ/mol, the heat of formation of Ca(OH)2 is -985.65 kJ/mol, the heat of solution of CaCl2 is -875.07 kJ/mol and the heat of formation of CaCl2 is -797.46 kJ/mol. Q = kJ/mol

Explanation / Answer

Find number of moles = V x M where V = 0.025L and M = 0.060
This number of moles is then present in 100 mL
So find the new molarity (the number of moles that would be in 1L)
For example, if the Molarity of Ca(OH)2 is 0.05 mole/L (and I have made this value up), then the [OH-] will have a concentration of 2 x 0.05 = 0.1 mole/L
You can either then use the ionic product for water, Kw = [H+(aq)][OH-(aq)] = 10-14 mole2L-2 to find [H+(aq)] and then use pH = -log[H+(aq)] to find pH
Or you can find pOH with a similar equation : pOH = -log[OH-(aq)].
Then pH + pOH = 14

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