I did a hydrate lab in school and these were my results and at the end we have to write the correc formula for the hydrate but I know the answer at the end is supposed to be 5H2O so why do I keep getting 4H2O? Can someone double check my work
Mass of evaporating dish 35.88
Mass of Dish and hydrated chemical 39.46
Calculated mass of hydrated chemical only 3.58
Mass of dish and chemical after 1st heating 38.40
Mass of dish and chemical after 2nd heating 38.40
Mass of dish and chemical after 3rd heating (if needed)
Now calculate the following:
Mass of anhydrous chemical only 38.40-35.88= 2.52 g
Mass of water lost. 1.06 g
% of hydrate the anhydrous chemical is. 2.52/3.58= 70.39%
Molar Mass of anhydrous Copper (II) sulfate 159. 6
226.7
Molar weight of water lost 67.2
Total number of moles of water
226.7-159.6= 67.1 67.1/18.02= 3.723 mols= 4
Prefix
tetra
Correct formula for the hydrate
CuSo4 4H20
Mass of evaporating dish: 35.88 g
MAss of dish and hydrated chemical
39.46 g
Calculated mass of hydrated chemical only
3.58 g
Mass of dish and chemical after 1st heating
38.40
Mass of dish and chemical after 2nd heating
38.40
Mass of anhydrous chemical only
38.40-35.88= 2.52 g
Mass of water lost
3.58-2.52= 1.06 g
% of hydrate the anhydrous chemical is
2.52/3.58= 70.39%
Mollar mass of anhydrous copper (II) sulfate: 159.6 grams
Molar mass of hydrated sopper (II) sulfate: 159.6/.7039 = 226.7 g
Molar weight of water lost: 226.7-159.6= 67.2
Total number of moles of water
67.1/ 18.02 = 3.723 which is about 4 mols
Prefix: tetra
formula for hydrate: CuSO4 4H20
WHERE DID I GO WRONG??? ITS really supposed to be 5H2O
Mass of water lost
3.58-2.52= 1.06 g
% of hydrate the anhydrous chemical is
2.52/3.58= 70.39%
Mollar mass of anhydrous copper (II) sulfate: 159.6 grams
Molar mass of hydrated sopper (II) sulfate: 159.6/.7039 = 226.7 g
Molar weight of water lost: 226.7-159.6= 67.2
Total number of moles of water
67.1/ 18.02 = 3.723 which is about 4 mols
Prefix: tetra
formula for hydrate: CuSO4 4H20
WHERE DID I GO WRONG??? ITS really supposed to be 5H2O
Prefix: tetra
formula for hydrate: CuSO4 4H20
WHERE DID I GO WRONG??? ITS really supposed to be 5H2O
I had the same problem to. It could have been due to the loss of water of crystallization to the atmosphere before the sample was heated. In my case, I got a trihydrate.
To double-check your work, let's go through the calculations step by step:
1. Mass of anhydrous chemical only:
This calculation is correct. 39.46 g (mass of dish and hydrated chemical) - 35.88 g (mass of evaporating dish) = 3.58 g.
2. Mass of water lost:
This calculation is correct. 39.46 g (mass of dish and hydrated chemical) - 38.40 g (mass of dish and chemical after 1st heating) = 1.06 g.
3. % of hydrate the anhydrous chemical is:
This calculation is correct. 2.52 g (mass of anhydrous chemical only) / 3.58 g (calculated mass of hydrated chemical only) = 70.39%.
Now, let's move on to determining the correct formula for the hydrate:
4. Molar Mass of anhydrous Copper (II) sulfate:
You provided two numbers (159.6 and 226.7) without specifying which one is the molar mass. Assuming 159.6 is the correct molar mass, we'll use that.
5. Molar weight of water lost:
The molar mass of water is 18.02 g/mol. To calculate the molar weight of water lost, we need to divide the mass lost (1.06 g) by the molar mass of water:
1.06 g / 18.02 g/mol = 0.0589 mol.
6. Total number of moles of water:
The mass of water lost (1.06 g) corresponds to 0.0589 mol. Therefore, the total number of moles of water in the hydrate is 0.0589 mol.
7. Prefix:
To determine the prefix for the hydrate, we need to find the ratio between the anhydrous chemical and water. Since the anhydrous chemical is CuSO4 and the moles of water is 0.0589 mol, the ratio is approximately 1:1. Hence, the prefix is "mono-".
8. Correct formula for the hydrate:
Combining the prefix and the formula for the anhydrous chemical, the correct formula for the hydrate is CuSO4•H2O.
Based on the information provided, it seems that the correct formula for the hydrate is CuSO4•H2O rather than CuSO4•4H2O as you initially mentioned.