I have solved the following question but i am not sure whether it is right or wrong..
Calculate the molar heat of reaction for the NaOH(aq) using the data obtained from this experiment. (this is a neutralization question)
H2so4
Volume= 30ml
Concentration=1.0mol/l
Initial temp. = 29.9
NAOH
Volume= 50ml
C = 1.0 mol/L
Initial temp. = 29
Final temp of the two contents = 32.9
This is my solution:
El = Eg
NaOH H2O
nH = mc∆t
0.05mol x H = 0.08L x 4.19 x 3.9
H = 26.15
The standard molar heat of neutralization of sodium hydroxide,
is -57 kJ/mol.
so shouldn't my calculated value be close to the standard value? Please tell me whether my solution is right or wrong!
Thank you in advance =)
1. Yes, I think the value should be closer to the standard listed.
2. I think you should take into account that the temperature of the NaOH and the H2SO4 were not the same initially.
[50 x 4.184 x (32.9-29.0)] + [30 x 4.184 x (32.9-29.9)] = 1,192 joules or 1.192 kJ.
1.192 kJ/0.05 mol = 23.8 kJ/mol but that isn't much improvement.
could it be that H needs to be negative??
To check whether your solution is correct, we can calculate the molar heat of reaction for the given neutralization reaction and compare it with the standard value.
The molar heat of reaction (∆Hrxn) can be calculated using the formula:
∆Hrxn = q / n
Where q is the heat absorbed or released in the reaction, and n is the number of moles of the limiting reagent (in this case, it is the sodium hydroxide, NaOH).
From the given data, we can calculate the heat (q) using the formula:
q = mc∆T
Where m is the mass of the solution (in this case, it can be calculated by multiplying the volume of the solution by its density), c is the specific heat capacity of the solution, and ∆T is the change in temperature.
Let's calculate the values step by step:
1. Calculate the mass of the solution:
Given
- Volume of H2SO4 = 30 ml
- Concentration of H2SO4 = 1.0 mol/L
Density of H2SO4 = 1.84 g/ml
Mass of H2SO4 = Volume x Density = 30 ml x 1.84 g/ml
2. Calculate the mass of the NaOH solution:
Given
- Volume of NaOH = 50 ml
- Concentration of NaOH = 1.0 mol/L
Density of NaOH = 1.0 g/ml
Mass of NaOH = Volume x Density = 50 ml x 1.0 g/ml
3. Calculate the total mass of the solution:
Total mass = Mass of H2SO4 + Mass of NaOH
4. Calculate the heat (q):
Given
- Initial temperature = 29.9 °C
- Final temperature = 32.9 °C
- Specific heat capacity of the solution (assuming it's the same for both solutions) = 4.19 J/g°C
q = mc∆T
q = (Total mass) x (specific heat capacity) x ∆T
5. Calculate the number of moles of NaOH:
Given
- Concentration of NaOH = 1.0 mol/L
- Volume of NaOH = 50 ml
n = Concentration x Volume / 1000
n = (Concentration) x (Volume) / 1000
6. Calculate the molar heat of reaction (∆Hrxn):
∆Hrxn = q / n
Now, plug in the calculated values into the formula to get the final answer.
By following these steps, you can verify if your solution is correct or if there was an error in your calculation. Let me know if you need further assistance!