Dissolving calcium hydroxide (∆Hsoln = -16.2 KJ/mol) in water is an exothermic process. How much lithium hydroxide (∆Hsoln = -23.6 KJ/mol) is needed to deliver the same amount of heat as 15.00 g of Ca(OH)2?
Hello everyone, thank you for taking a look at my question. I would be most appreciative if you could give me advice on how to solve this problem. I've exhausted myself trying to solve it and I am not getting anywhere. I'm not asking that you give me the answer, but can you tell me the steps I can take to solve it. Thank you!
mols Ca(OH)2 = grams/molar mass = approx 0.2 but you need a better number than that.
How much heat was released for the 15 g Ca(OH)2? That is
16.2 kJ/mol x approx 0.2 mol = approx 3 kJ.
So you need approx 3 kJ from the LiOH. How many mols do you need?
23.6 x # mols LiOH = approx 3.
Solve for # mols, then
grams LiOH = mols LiOH x molar mass LiOH.
Thank you Dr. Bob.
This is my work:
15g / 74.093 g Ca(OH)2 = 0.202
16.2 kJ/mol * 0.202 = 3.272 kJ
23.6 kJ/mol * X mol LiOH = 3.272 KJ
X mol LiOH = 0.138
0.138 * 23.95 = 3.32 g LiOH
To solve this problem, you can use the concept of heat of solution (∆Hsoln) to calculate the amount of lithium hydroxide needed to deliver the same amount of heat as 15.00 g of calcium hydroxide.
Here are the steps to solve the problem:
1. Convert the given mass of calcium hydroxide (Ca(OH)2) to moles. To do this, divide the mass by the molar mass of calcium hydroxide.
2. Determine the heat change (∆H) for dissolving 1 mole of calcium hydroxide in water (∆Hsoln). It is given as -16.2 kJ/mol.
3. Use the molar ratio of calcium hydroxide and lithium hydroxide to calculate the moles of lithium hydroxide needed. The ratio can be obtained from the balanced chemical equation:
Ca(OH)2 + 2LiOH → Ca(OH)2 + 2LiOH
Since 1 mole of calcium hydroxide reacts with 2 moles of lithium hydroxide, the number of moles of lithium hydroxide needed will be twice the number of moles of calcium hydroxide.
4. Multiply the moles of calcium hydroxide (obtained in step 1) by the molar ratio (2) to calculate the moles of lithium hydroxide needed.
5. Finally, convert the moles of lithium hydroxide to grams by multiplying the moles by the molar mass of lithium hydroxide.
Please let me know if you need help with any specific step or if you have any further questions!
To solve this problem, there are a few steps you can follow:
Step 1: Calculate the number of moles of Ca(OH)2 in 15.00 g of the compound.
- The molar mass of Ca(OH)2 is calculated by adding the atomic masses of each element: Ca (40.08 g/mol), O (16.00 g/mol), H (1.01 g/mol).
- The molar mass of Ca(OH)2 is 40.08 g/mol + 2(16.00 g/mol) + 2(1.01 g/mol) = 74.09 g/mol.
- To find the number of moles, divide the given mass (15.00 g) by the molar mass (74.09 g/mol).
Step 2: Use the molar ratio between Ca(OH)2 and LiOH to determine the number of moles of LiOH needed.
- The balanced chemical equation for the reaction between Ca(OH)2 and LiOH is:
Ca(OH)2 + 2LiOH → Ca(OH)2 + 2LiOH
- From the equation, you can see that 1 mole of Ca(OH)2 reacts with 2 moles of LiOH.
- Multiply the number of moles of Ca(OH)2 from step 1 by the molar ratio of LiOH to Ca(OH)2.
Step 3: Calculate the mass of LiOH required to deliver the same amount of heat as 15.00 g of Ca(OH)2.
- The molar mass of LiOH is calculated by adding the atomic masses of each element: Li (6.94 g/mol), O (16.00 g/mol), H (1.01 g/mol).
- The molar mass of LiOH is 6.94 g/mol + 16.00 g/mol + 1.01 g/mol = 23.95 g/mol.
- To find the mass of LiOH, multiply the number of moles of LiOH from step 2 by the molar mass of LiOH.
By following these steps, you should be able to calculate the mass of LiOH required to deliver the same amount of heat as 15.00 g of Ca(OH)2.