Formula Calculation

Formula Calculation

Empirical Formula Calculation

• We have a compound that is 32.38% Na, 22.65% S, 44.99% O

• Determine the empirical formula

Empirical Formula Calculation

• First step: Change our 100% composition to 100 g

• We get 32.38 g Na, 22.65g S, 44.99g O

Empirical Formula Calculation

• Step two: convert each of these to moles

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Multiple Choice

Choose how many moles of Na, S, O.

• 1.408 mol Na, .7063 mol S, 2.812 mol O

• 1.5 mol Na, 1 mol S, 3 mole O

• 2 mol Na, 1 mol S, 4 mole O

• 3 mol Na, 2 mol S, 2 mol O

Empirical Formula Calculation

• To figure out moles we will divide by the molar mass of each

• Next we have to determine the ratios

• How will we do this?

Multiple Choice

What is the mol ratio of Na,S,O?

• 4,2,8

• 2,1,4

• 1,1,2

• 1,1,1

Multiple Choice

What is our Empirical Formula?

• Na₄S₂O₈

• Na_1.4S_.7O_2.8

• Na₂SO₄

Determining Molecular Formula

• Now lets figure out the molecular formula- the actual number of each atom in a compound

Determing Molecular Formula

• An experimental compound with the empirical formula NCl_3, has a molar mass of 361.5 g/mol

• What is the molecular formula?

Multiple Choice

A compond is 38.6% K, 13.8% N, and 47.6% O. Determine the Empirical Formula

• KN₂O₃

• K₂NO₃

• KNO₃

Multiple Choice

A compound has the empirical formula of P₂O₅. It has the molar mass of 284 g/mol. What is the molecular formula?

• P₂O₁₀

• P₄O₂₀

• P₄O₁₀