When a 3.25 g sample of solid sodium hydroxide was dissolved in a calorimeter in 100 g of water, the temperature rose from 23.9 C to 32.0 C. Calculate delta H (in kJ/mol) of for the solution process:
NaOH (s) -> Na+(aq) + OH-(aq)
Use a calorimeter heat capacity of Ccal = 15.8 J/degrees C.
A 50 mL sample of a 1.00 M solution of CuSO4 is mised with 50 mL of 2.00 M KOH in a calorimeter. The temperature of both solutions was 20.2 C before mixing and 26.3C after mixing. The heat capacity of the calorimeter is 12.1 J/K. From this data, calculate the delta H for the process:
CuSO4(1 M) + 2KOH(2 M) - Cu(OH)2(s) + K2SO4(0.5 M)
Didn't I do this problem last night?
q = (mass H2O x specific heat H2O x delta T) + (Ccal*delta T).
q/3.25 = delta H in J/g
(q/3.25)* molar mass NaOH = delta H in J/mol
Then convert to kJ/mol.
41.7
Oh boy, we've got some chemistry questions here! Let's see if I can add a little humor to the mix while trying to answer them.
For the first question, we can use the equation q = mcΔT to calculate the heat absorbed by the solution. Since the calorimeter heat capacity is given, we need to consider that as well. The heat absorbed by the solution can be equal to the heat absorbed by the calorimeter. So we have:
q(solution) + q(calorimeter) = 0
Now, let's calculate the q(solution):
q(solution) = m(solution) * c(solution) * ΔT
The mass of the solution can be calculated by adding the mass of the sodium hydroxide and the mass of water. The heat capacity of water (c) is 4.18 J/g°C. And of course, don't forget to convert grams to kilograms so we can get the answer in kJ/mol. Phew, that was a mouthful!
As for the second question, we have a lovely mixing process going on. We can use the equation q = mcΔT again to calculate the heat absorbed or released by the system. Since we have two solutions mixing, we need to consider their volumes and concentrations. Hey, it's like a chemistry cocktail party!
To find the moles of each substance, we can use the equation:
moles = volume (in liters) * concentration (in moles/liter)
Now, let's calculate the q for the system using the same equation as before. And remember to convert grams to kilograms and milliliters to liters. Phew, this chemistry stuff requires some mental gymnastics!
I hope my clownish attempts at explaining these calculations didn't make you feel like this is all a circus act. Good luck with your chemistry endeavors, and don't forget to add a pinch of humor along the way!
To solve both of these questions, we need to use the equation:
q = m * C * ΔT
where q is the heat exchange (in joules), m is the mass (in grams), C is the heat capacity (in J/degrees C), and ΔT is the change in temperature (in degrees C).
Let's solve these questions step by step:
Question 1:
1. First, we need to calculate the heat exchanged (q) by the reaction. We can use the equation q = m * C * ΔT.
q = (mass of water + mass of sodium hydroxide) * Ccal * ΔT
q = (100 g + 3.25 g) * 15.8 J/degrees C * (32.0 C - 23.9 C)
2. Next, we need to convert the heat exchanged (q) to kilojoules (kJ). Since 1 kJ = 1000 J, we divide q by 1000.
q(kJ) = q(J) / 1000
3. Finally, we need to calculate the number of moles of sodium hydroxide (NaOH) in the reaction.
moles of NaOH = mass of NaOH / molar mass of NaOH
4. To find ΔH (enthalpy change) per mole, we divide q(kJ) by the number of moles of NaOH.
ΔH (in kJ/mol) = q(kJ) / moles of NaOH
Question 2:
1. Similarly, we need to calculate the heat exchanged (q) by the reaction using the equation q = m * C * ΔT.
q = (mass of water + total mass of reactants) * Ccal * ΔT
q = (100 g + 50 mL*1.00 g/mL + 50 mL*2.00 g/mL) * 12.1 J/K * (26.3 C - 20.2 C)
2. Convert the heat exchanged (q) to kilojoules (kJ) by dividing q by 1000.
q(kJ) = q(J) / 1000
3. Find the number of moles of CuSO4 and KOH in the reaction.
moles of CuSO4 = volume of CuSO4 * concentration of CuSO4
moles of KOH = volume of KOH * concentration of KOH
4. Calculate the number of moles of Cu(OH)2 formed and K2SO4 consumed.
moles of Cu(OH)2 formed = moles of KOH / 2
moles of K2SO4 consumed = moles of CuSO4 / 1
5. Calculate ΔH (enthalpy change) per mole by dividing q(kJ) by the moles of Cu(OH)2 formed.
ΔH (in kJ/mol) = q(kJ) / moles of Cu(OH)2 formed
Remember to convert any necessary units during calculations, such as converting mL to grams or adjusting concentrations to correct units.