When 3.761g of a hydrate of strontium chloride is heated to 60 degree C it forms strontium chloride dihydrate of mass 2.746g What is the formula of the original sample?

SrCl2.xH2O ==> SrCl2.2H2O + xH2O

3.761g.........2.746g.......1.015g
(3.761-2.746 = 1.015g).
I would then convert SrCl2.2H2O to SrCl2 which can be done as follows:
2.746g x (molar mass SrCl2/molar mass SrCl2.2H2O) = 2.746 x (158.53/194.56) = 2.237 g SrCl2.

Now convert 2.237 g SrCl2 to moles and convert 1.015 g H2O to moles.

moles SrCl2 = grams/molar mass = about 0.014 but you need to do it more accurately.
moles H2O = 1.015/about 18 = about 0.056

Now find the ratio of SrCl2 to H2O this way. Divide the smaller number by itself which assures that number of being 1.000.
0.014/0.014 = 1.000
0.056/0.014 = 4.00
When you do this more accurately you may not end up with such even numbers; if so, round to whole numbers. You would write the formula as
SrCl2.4H2O

Well, it seems like the strontium chloride went on a hydrate diet! It must have lost some water weight when it was heated to 60 degrees C. So, let's look at the numbers. Initially, we had 3.761g of the original hydrate, and after heating, we were left with 2.746g of strontium chloride dihydrate.

To find the mass of water lost, we subtract the mass of the final strontium chloride dihydrate from the mass of the original hydrate: 3.761g - 2.746g = 1.015g.

Since water has a molar mass of approximately 18g/mol and the mass of the water lost is 1.015g, we can calculate the number of moles lost: 1.015g / 18g/mol ≈ 0.056 moles.

Now, let's find the number of moles of strontium chloride dihydrate formed. The mass of the final product is 2.746g, and the molar mass of strontium chloride dihydrate is approximately 158g/mol. So, the number of moles of strontium chloride dihydrate formed is 2.746g / 158g/mol ≈ 0.0174 moles.

Based on the ratio of moles, we can determine the formula of the original sample. Dividing the number of moles of water lost by the number of moles of strontium chloride dihydrate formed, we get approximately 0.056 moles / 0.0174 moles ≈ 3.218.

Rounding to the nearest whole number, we get 3. Hence, the formula of the original sample is SrCl2∙3H2O. So, the original sample was strontium chloride trihydrate.

To determine the formula of the original sample, we need to calculate the number of moles of strontium chloride and the number of moles of water in the hydrate.

Step 1: Calculate the number of moles of strontium chloride dihydrate.
The molar mass of strontium chloride dihydrate (SrCl2•2H2O) is:
1 strontium atom (Sr) = 1 * 87.62 g/mol = 87.62 g/mol
2 chlorine atoms (Cl) = 2 * 35.45 g/mol = 70.90 g/mol
2 water molecules (2H2O) = 2 * [2 * (1.01 g/mol) + 16.00 g/mol] = 2 * 18.02 g/mol = 36.04 g/mol

The total molar mass of strontium chloride dihydrate is:
87.62 g/mol + 70.90 g/mol + 36.04 g/mol = 194.56 g/mol

To calculate the number of moles of strontium chloride dihydrate, divide its mass by its molar mass:
2.746 g / 194.56 g/mol = 0.0141 mol

Step 2: Calculate the number of moles of water.
From the formula of strontium chloride dihydrate (SrCl2•2H2O), we know that there are 2 moles of water for every 1 mole of strontium chloride dihydrate. Therefore, the number of moles of water is twice the number of moles of strontium chloride dihydrate:
0.0141 mol * 2 = 0.0282 mol

Step 3: Calculate the number of moles of strontium chloride.
To calculate the number of moles of strontium chloride, subtract the number of moles of water from the total number of moles of the original sample:
0.0141 mol - 0.0282 mol = -0.0141 mol

Step 4: Determine the formula of the original sample.
Since we obtained a negative number of moles for strontium chloride, it means that there was no strontium chloride in the original sample. Therefore, the formula of the original sample is H2O, indicating that it was just water without any added strontium chloride.

So, the formula of the original sample is H2O.

To determine the formula of the original sample, we need to calculate the molar ratio between strontium chloride and water in the given hydrate compound.

First, we need to find the number of moles of the products formed during the heating process:

1. Calculate the number of moles of strontium chloride dihydrate formed:
- Mass of strontium chloride dihydrate = 2.746 g
- Molar mass of strontium chloride dihydrate = molar mass of strontium (Sr) + 2*(chlorine's molar mass (Cl)) + 2*(molar mass of water (H2O))
- The molar mass of strontium (Sr) is found on the periodic table, and the molar mass of chlorine (Cl) is 35.45 g/mol. The molar mass of water (H2O) is 18.015 g/mol.
- Calculate the molar mass of strontium chloride dihydrate: molar mass = molar mass of Sr + 2*(molar mass of Cl) + 2*(molar mass of H2O)
- Convert the mass of strontium chloride dihydrate to moles using the formula: moles = mass / molar mass

Next, we need to find the mole ratio between strontium chloride and water:

2. Calculate the number of moles of water released:
- The difference in mass before and after heating represents the mass of water released during the heating process. In this case, the mass of water released is the difference between the mass of the original hydrate and the mass of the strontium chloride dihydrate.
- Mass of water released = mass of the original hydrate - mass of strontium chloride dihydrate
- Convert the mass of water released to moles using the formula: moles = mass / molar mass

Now that we have the number of moles of strontium chloride dihydrate and the moles of water released, we can calculate the mole ratio.

3. Determine the mole ratio:
- Divide the number of moles of water released by the number of moles of strontium chloride dihydrate.
- This will give us the ratio between water and strontium chloride.

The final step is to determine the formula of the original hydrate compound based on the mole ratio:

4. Write the formula of the original hydrate:
- Using the mole ratio, we can determine the number of water molecules associated with each formula unit of strontium chloride.
- The formula of the hydrate compound is typically written as: A.xH2O, where A represents the anhydrous compound and x represents the number of water molecules.

By going through these steps, we can calculate the molar ratio and determine the formula of the original hydrate compound.