When 2.5000g of NaOH were dissolved in 49.0g water in a calorimeter at 24.0C, th
ID: 795866 • Letter: W
Question
When 2.5000g of NaOH were dissolved in 49.0g water in a calorimeter at 24.0C, the temperature of the solution went up to 37.1C.
a) is this dissolving process exothermic? yes or no?...... yes
b)Calculate qH2O using q= (sp x m x deltaT) .......... 2685.7096 J (2.68x10^3)
c) Calculate the mass of the solution (NaOH + H2O).......... 51.5g
d) find qrxn for the entire reaction (water and NaOH) as it occured in the calorimeter. use q rxn = q soultion = delta H reaction........ -2822.73 J or -2.82x10^3
e) find qrxn (using part d) for the dissolving of 1.00g NaOH in water.
f) find delta H rxn (using part e) for the dissolving of 1.00 mole of NaOH in water.
I only need help on e and f, but I put the rest of the question up anyway. THANK YOU!
thank you so much for your help! please show how you got your answer!!!!
Explanation / Answer
a)
Yes,because heat energy is liberated so the process is exothermic.
b)
We shall use the formula Q = mct
where m is the mass of the water
c is the specific heat capacity of water
and t is the change in temperature of the water
Q = (49)(4.18 J)(37.1 - 24.0)
= 2683.14 J
c)
Mass of solution = Mass of H20 + Mass of NaOH
= 49 g + 2.5 g
= 51.5 g
d)
Q = mct
Q = (2.5 + 49)(4.18)(37.1 - 24)
= 2820.037 J (dH reaction)
e)
The dissolution of 2.5 g of NaOH produces 2820.037 J of heat energy
Therefore, the amount of heat energy produced when 1g of NaOH is dissolved
= (2820.037)/2.5
= 1128.0148 J
dH = 1128.0148 J/g
f) Relative Formula Mass(RFM) of NaOH = 40
40g = 1 mole of NaOH
2.5g = 2.5/40
= 0.0625 moles of NaOH
The dissolution of 0.0625 moles of NaOH produces 2820.037 J of heat energy.
Therefore, the amount of heat energy produced when 1 mole of NaOH is dissolved
= (2820.037)/0.0625
= 45120.592 J
dH = 45120.592 J/mol
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