Chem Unit 8 Quick Review

Chem Unit 8 Quick Review

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Multiple Choice

To find the Empirical Formula:

1. Convert the %s to grams

2. Convert Grams to Moles

3. _____________________

• Find the molar mass and divide by it

• Use the smallest # of moles to set up mole ratios for the remaining elements

• Use the smallest atomic mass to set up molar ratios for the remaining ratios.

Multiple Choice

What is the _____________________ of a compound found to contain 75.0% carbon and 25.0% hydrogen by mass?

• Mass Percent

• Mass Percent of a Hydrate

• Empirical Formula

• Molecular Formula

Fill in the Blanks

SOLVE IT: What is the empirical formula of a compound found to contain 75.0% carbon and 25.0% hydrogen by mass?

Multiple Choice

To find the mass percent:

1. Find the Molar Mass

2. ______________________

3. Multiply by 100

• Multiply the molar mass by each individual element's atomic mass

• Divide each element's individual atomic mass by the molar mass

• Divide the molar mass by the lowest molar ratio

Multiple Choice

Calculate the _____________ of each element in ammonia, NH₃.

• Mass Percent

• Mass Percent of a Hydrate

• Empirical Formula

• Molecular Formula

Fill in the Blanks

Solve it: Calculate the Mass Percent Nitrogen in NH₃. Round your answer to the nearest tenth place.

Multiple Choice

To solve for the molecular Formula:

1. Find the molar mass of the compound

2. __________________________

3. Multiply each subscript by your answer to #2.

• Multiply by each element's atomic mass by the molar mass

• Divide the experimental mass (given in the problem) by the molar mass

• Multiply the experimental mass (given in the problem) by the molar mass

Multiple Choice

The empirical formula for a compound is P2O5. Its experimental molar mass is 284 g/mol. Determine the ____________________ of the compound.

• Mass Percent

• Mass Percent of a Hydrate

• Empirical Formula

• Molecular Formula

Fill in the Blanks

The empirical formula for a compound is P₂O₅. Its experimental molar mass is 284 g/mol. Determine the molecular formula of the compound.