Empirical Formula LabEmpirical: based on evidence

Empirical Formula: simplest whole-number combination of elements in that compound

Molecular Formula: actual whole-number ratio between the elements in that compound (real thing)

C6H12O6 CH2O

Both represent the same compound

Molecular formula Empirical formula

So what are we trying to do?By figuring out how much zinc and chlorine are in our product (zinc chloride), we hope to determine the molar ratio between the two elements

𝑚𝑜𝑙𝐶𝑙𝑚𝑜𝑙 𝑍𝑛

Because the amount of particles in a mole is the same for Cl and Zn, we should be able to use this ratio to determine the simplest ratio of Cl to Zn in our compound of zinc chloride

Things we need…..• Mass of Zn in product-we will assume ALL of the zinc we had at the beginning successfully reacted so the amount of zinc in our product should be the same as the amount of zinc we started with• Mass of product-we don’t want to scrape out the product because we don’t want to leave any product behind. Because of this, we will need the mass of the beaker alone and subtract is from the beaker + product mass• Mass of chlorine in product-if we know the mass of the product & the mass of zinc in product, then we should be able to subtract the mass of zinc from the mass of product to get the mass of chlorine

Zinc begins to react with hydrochloric acid (HCl)• Inside the bubbles is hydrogen gas (H2)

Zn and HCl are placed on a hot plate to speed up the reaction

When the reaction is complete and there is no more HCl left• What remains is your

zinc chloride product• Zinc chloride has a

special property that allows it to “take in” water from the air so it’s constantly “soupy”

• We don’t want this water involved in our product…

In order to remove excess water, we boil it off• Being very careful

not to burn our product!!!

Determine the molecular formulaThe empirical formula of a compound is NO2. Its molecular weight is 92 g/mol. What is its molecular formula?

The empirical formula of a compound is CH2. Its molecular weight is 70 g/mol. What is its molecular formula?

Using % composition to determine empirical formula

Find the empirical formula for a compound consisting of 63% Mn and 37% O

Determining the molecular formulaDetermine the molecular formula of a compound that contains 40% C, 6.72% H, and 53.29% O• Molecular weight of this compound is 180 g/mol

A compound is found to contain 40% carbon, 6.7% hydrogen, and 53.5% oxygen. Its molecular weight is 60 g/mol. What is its molecular formula?

NutraSweet has the following chemical composition Carbon: 57.14%

Hydrogen: 6.16%Nitrogen: 9.52%Oxygen: 27.18%

Calculate the empirical formula of NutraSweet and find the molecular formula• The molecular weight of NutraSweet is 294.3 g/mol

Complete the following problemAfter performing an experiment involving the reaction between calcium and bromine, a lab group recorded the following data.

Mass of calcium (g) 1.6

Mass of product CaxBry 8

Using this data, determine the empirical formula of the compound between calcium and bromine