pH scale is used to measure the acidity or alkalinity on a scale of 0-14 where 0-6.9 is the acidic region , 7.1-14 is the basic region and 7 is for the neutral substance. We can calculate the concentration of proton from pH.
where is the concentration of proton
As per the question ,the pH of coffee is 5.6 and we need to find the concentration of proton so putting the values in the above equation, we get
Answer 1) : When we calculate the ΔQ = -40.66 kJ (heat of vaporisation).
Then, we can relate the work done with this equation,
ΔW = -PΔV
First we need to calculate the volume, which will be,
Volume of water vapor = (nRT) / (P)
Then, V = (1 mole) X (0.0821 L X atm/mole X K) X (373.15K) / (1atm) = 30.6 liters So, it is given, and verified.
Volume of Water can be used for finding the; Density = M / V
D = ( 1 mole) X (18.02 g/mole) / (18.80 mL) = 0.9585 g/mL
On, substituting the values, we get,
ΔW = -PΔV
Work = - (1 atm) X (0.00188L - 30.62L) X 0.1013kJ/L X atm = 3.10 kJ
hence the work done is 3.10 kJ
Answer 2) Now, for calculating the internal energy, we can use the formula as,
ΔE = ΔQ + ΔW
Here, we have the values of ΔQ = -40.66 kJ and ΔW as = 3.10 kJ
So, we get, ΔE = (-40.66) + (3.10) = - 37.55 kJ
Therefore, the change in the internal energy will be -37.55 kJ.
