When pure sulfuric acid is dissolved in water,heat is evolved.To a calorimeter containing 300g of water at 20degree C,10.65g of sulfuric acid also added at the same temperature.The change in temperature,which was monitored by a digital probe with negligible heat capacity ceased when it reaches 26.55 degree C.If specific heat of mixture is 4.184 J/g.K and small heat capacity of calorimeter ignored,what is the heat evolved/mole of sulfuric acid? I did this question and I got -75.7kJ/mole. I would like to know if my answer is correct. Thanks
Looks good to me.
But in the answer options:
a) -27.4 kJ
b) -72.8 kJ
c) -78.4 kJ
d) -84.6kJ
I attempted this problem in the other way.When using the q =mcdT,I added the mass of both water and sulfuric acid.
q = (300g +10.65g)(4.184J/g.K)(6.55C)
= 8513.43 J
Then, I calculated the mole of sulfuric acid ,n = 10.65g/(98.08g/mol) = 0.1086mol
Since the question asks for heat evolved/mole of H2SO4,so
q sulfuric acid = 8513.43J/(0.1086mol)x 1 mol of H2SO4
= -78.4 kJ(option c)
Need detailed explanation.Thank you.
I also got -78.4kjmol^-1. Is this correct?
To find the heat evolved per mole of sulfuric acid, we can use the formula:
Heat evolved = (specific heat of mixture * mass of water * change in temperature) / moles of sulfuric acid
Let's calculate the variables step by step:
1. Specific heat of mixture: The specific heat capacity of the mixture is given as 4.184 J/g.K.
2. Mass of water: 300g of water was used in the calorimeter.
3. Change in temperature: The initial temperature of water is 20°C, and it reaches 26.55°C. So the change in temperature is (26.55 - 20) = 6.55°C.
4. Moles of sulfuric acid: To calculate the moles of sulfuric acid, we need to know its molar mass. The molar mass of H2SO4 is:
2(1.01 g/mol) + 32.07 g/mol + 4(16.00 g/mol) = 98.09 g/mol
To find moles of sulfuric acid, we can use the formula:
moles = mass / molar mass
For 10.65g of sulfuric acid:
moles = 10.65g / 98.09g/mol
Now, we can calculate the heat evolved:
Heat evolved = (4.184 J/g.K * 300g * 6.55°C) / (10.65g / 98.09g/mol)
Calculating this, we find that the heat evolved is approximately -75.8 kJ/mol (rounded to one decimal place).
Therefore, your answer of -75.7 kJ/mol is very close to the correct answer.