10/13/22 - Determining Formulas and Chemical Equations

Question 1

Given the masses of elements in a compound, how do you find the empirical formula?

Answer 1

1) Divide each mass (g) by the molar mass (g/mol) to get moles

2) Use the moles to write a preliminary formula

3) Divide each mole value by the smallest one

4) Multiply each of these by the smallest number that makes them all whole integers.

Question 2

Given the mass percent of elements in a compound, how do you find the empirical formula?

Answer 2

1) Turn % values into masses (25.61% –> 25.61 grams)

2) Divide these masses (g) by the molar mass (g/mol) to get moles

3) Use the moles to write a preliminary formula

4) Divide each mole value by the smallest one

5) Multiply each of these by the smallest number that makes them all whole integers.

Question 3

How do you turn empirical formulas into molecular formulas?

Answer 3

1) Divide the compound’s molar mass by the molar mass of the empirical formula.
2) Multiply the empirical formula by the resulting multiple.

Question 4

What are isomers?

Answer 4

Different compounds with the same molecular formula and molar mass, but different atom arrangements.

They can have different properties.

Question 5

What is a good strategy for balancing chemical equations?

Answer 5

Start with the most complex substance, end with the simplest.