The Formula Feud

Percent Composition

100

What is the percent composition of lithium in lithium oxide (Li₂O)?

Molar Mass of Li₂O= 29.8g/mol

Percent Composition:46.3%

200

Calculate the percent composition of carbon in carbon dioxide (CO₂). 

Percent Composition: 27.27%

300

Calculate the percent composition of phosphorus in magnesium phosphate Mg₃(PO₄)_2. 

Percent composition: 23.58%

400

Calculate the percent composition of oxygen in magnesium hydroxide.

Percent Composition: 54.89%

500

Calculate the percent composition of both carbon and hydrogen in acetamide (C₂H₅NO).

Percent composition for C: 40.668%

Percent composition for H: 8.533%

Empirical Formula

100

Given that a 95.2g sample contains 40.8g of carbon and 54.4g of Oxygen, determine the empirical formula

a)C₂O₂

b)CO₃

c)CO 

d)C₂O

Empirical Formula:

c)CO

200

Calculate the empirical formula of a compound that is 85.6% Carbon, and 14.4% Hydrogen. 

a)CH₂

b)CH

c)C₂H₄

d)C₂H

Correct Answer:

a) CH₂

300

Determine the Empirical Formula for a lactic acid that is 40.0% Carbon, 6.71% hydrogen, and 53.3% Oxygen. 

Empirical Formula

CH₂O

400

Write the empirical for a compound that is 21.20% Nitrogen, 6.06% Hydrogen, 24.30% Sulfur, and 48.45% Oxygen.

Empirical Formula: 

N₂H₈SO₄

500

A compound has 40.68% carbon, 5.12% hydrogen, and 54.20% oxygen. Calculate the empirical formula 

Empirical Formula:

C₂H₃O₂

Molecular Formula

100

What is the molecular formula for a compound with an empirical formula of C₂OH₄ and a molar mass of 44 g/mol. 

Molecular Formula:

C₂OH₄

200

What is the molecular formula for a compound with an empirical formula of C₄H₄O and molar mass of 136 g/mol. 

Molecular Formula:

C₈H₈O₂

300

The empirical formula of a compound is CH₂, its molar mass is 56 g/mol. Given this, find the molecular formula for this compound. 

Molecular Formula:

C₄H₈

400

Find the molecular formula for a compound with an empirical formula of CFBrO and a molar mass of 254.7 g/mol.

Molecular Formula:

C₂F₂Br₂O₂

500

What is the molecular formula of a compound containing 65.5% carbon, 5.5% hydrogen, and 29.0% oxygen, and a molar mass of 110 grams/mole?

BONUS for 100 pts* Determine the empirical formula and it's molar mass as well

Molecular Formula: C₆H₆O₂

Bonus* Empirical Formula: C₃H₃O with a mass of: 55 g/mol

True or False

100

True or False

The molecular formula for a compound can be the same as or a multiple of the compound's empirical formula.

True!

200

True or False

When writing an empirical formula where Carbon and Hydrogen are present, carbon comes first, then hydrogen, and finally the rest of the elements in alphabetical order.

True! 😁

300

This is the correct way of writing this empirical formula is C₂H₂0₆Ca₁

False! 😮Ca is a metal so it is written first

400

The formula for finding percent composition is:

(m_{element /} m_{compound) x 100%}

True

500

True or False

The empirical formula will always be greater than the molecular formula. 

False😮

Hydrates

100

True or false:

If a mole ratio is 1.5, you should round to 2

FALSE

200

A 19.87 g sample of a hydrate of magnesium carbonate (MgCO3 * ?H2O) was heated to drive off the water. The mass was reduced to 5.19 g. What is the mass of the water?

14.68 grams

300

A sample of Calcium oxide is found to have 0.5 moles of material left after heating. The water in the compound was found to be 2 moles. What is the empirical formula?

CaO * 4 H₂O

400

A 15.67 g sample of a hydrate of Barium carbonate (BaCO3 * ?H2O) was heated to drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate?

6 BaCO₃ * 7 H₂O

500

A 25 g sample of magnesium chloride hydrate (MgCl₂ * ? H₂O) was heated in a crucible. The mass remaining after the second heating was 13.25 grams. What is the chemical formula for the hydrate?

3 MgCl₂ * 14 H₂O