sometimes,instead of percentage composition, you will have the composition of a mass sample. using the actual mass of the sample, determine the empirical formula for compounds that have the following analyses.
b. a 13.07g sample of an unknown substance is composed of 9.48g of barium, 1.66g of carbon and 1.93g of nitrogen
c.0.0025 g sample of an unknown substance is composed of 0.0091g manganese, 0.0106g oxygen, and 0.0053 sulfur
c.
They are done the same way. Convert grams to mols and find the ratio.
To determine the empirical formula, you need to find the ratio of the elements in the compound. Here's how you can do it:
b. a 13.07g sample of an unknown substance is composed of 9.48g of barium, 1.66g of carbon, and 1.93g of nitrogen.
Step 1: Calculate the moles of each element in the sample.
- Moles of barium: 9.48g / atomic mass of barium
- Moles of carbon: 1.66g / atomic mass of carbon
- Moles of nitrogen: 1.93g / atomic mass of nitrogen
Step 2: Determine the smallest number of moles from the three elements calculated in Step 1. This will be the ratio used to determine the empirical formula.
Step 3: Divide the moles of each element by the smallest number of moles to get the simplest whole-number ratio.
Step 4: Round the ratios to the nearest whole number, if necessary, to obtain the empirical formula. The whole numbers obtained will represent the subscripts for each element in the compound.
c. 0.0025 g sample of an unknown substance is composed of 0.0091g of manganese, 0.0106g of oxygen, and 0.0053g of sulfur.
Follow the same steps as outlined above to determine the empirical formula using the mass of each element.
Remember, when calculating the moles, use the atomic mass of each element. You can find the atomic mass of elements on the periodic table.