How would you find the empirical formula for this... a substance was found by analysis to contain 20% by mass calcium and 80% by mass bromine.

Would it be CaBr2?

This is what I did...

50g Ca * 20 mol Ca/801.56g Ca = .499 mol Ca

80g Br * 80 mol Br/6392.32g Br = 1.001 mol Br

1.001/.499 = 2 so CaBr2

Yes, the answer is CaBr2 but I don't buy the way you obtained that formula. Did you just pull 50 g Ca and 80 g Br out of thin air? The proper way to work it is the way I showed you in your first post.

First we find the moles of each assuming that mixture is having total mass of 100 grams. So mass of Ca = 20 g and Br =80

Moles of Ca = 20 g/40.08 (g/mole)= 0.499 Mole

Moles of Br = 80 g/ 1.001 moles

So now we can find the molar ratio = 0.499/1.001 =1/2
That means Ca1Br2 so the empirical formula would be CaBr2.
This is absolutely right.

To find the empirical formula for the substance, you need to determine the ratio of the elements in terms of moles. The moles can be calculated using the given percentages and the molar masses of calcium (Ca) and bromine (Br).

Let's go through the steps:

1. Calculate the mass of calcium (Ca) in grams:
Mass of Ca = 20% * Total mass of the substance = 20g

2. Convert the mass of calcium to moles:
Moles of Ca = Mass of Ca / Molar mass of Ca = 20g / 40.08 g/mol = 0.499 mol

3. Calculate the mass of bromine (Br) in grams:
Mass of Br = 80% * Total mass of the substance = 80g

4. Convert the mass of bromine to moles:
Moles of Br = Mass of Br / Molar mass of Br = 80g / 79.90 g/mol = 1.001 mol

5. Divide the moles of bromine by the moles of calcium to determine the ratio:
Ratio = Moles of Br / Moles of Ca = 1.001 mol / 0.499 mol ≈ 2

From the ratio, we can conclude that the empirical formula of the substance is CaBr2, indicating that there are two bromine atoms for every one calcium atom. Your initial assumption is correct!

To find the empirical formula of a substance, you need to determine the ratio of the elements present in the compound. In this case, the substance contains 20% calcium (Ca) and 80% bromine (Br) by mass.

First, assume you have a 100g sample of the substance. That means you have 20g of calcium and 80g of bromine.

Next, convert the mass of each element into moles by dividing it by its molar mass. The molar mass of calcium (Ca) is 40.08 g/mol and the molar mass of bromine (Br) is 79.9 g/mol.

For calcium:
20g Ca * (1 mol Ca / 40.08g Ca) = 0.499 mol Ca

For bromine:
80g Br * (1 mol Br / 79.9g Br) = 1.001 mol Br

Since you want to find the ratio of calcium to bromine, divide the number of moles of bromine by the number of moles of calcium:
1.001 mol Br / 0.499 mol Ca ≈ 2

This means that for every one mole of calcium, there are approximately two moles of bromine. Therefore, the empirical formula for the substance is CaBr2, as you correctly determined.