Kennedy--1 step Stoichiometry conversions

Stoichiometry conversions

Stoichiometry

Stoichiometry comes from two Greek root words
"Stoichio" means elements
"metry" means measure

The numerical relationship between different elements and different units.

​Molar mass: the relationship between the mole and mass

We already learned about molar mass in the last unit. This is the mass in grams of 1 mole or 6.02x10²³ particles of an element or a compound.


Let's do some practice problems to review.

Multiple Choice

What is the molar mass of silver (Ag)?

• 107.87 g/mol

• 47 g/mol

• 14 g/mol

• 28.06 g/mol

Multiple Choice

What is the molar mass of CaCO₃?

• 95.30 g/mol
• 102.45 g/mol
• 98.00 g/mol
• 100.09 g/mol

​The molar mass can be used to convert between moles and grams

grams = moles x molar mass


moles = grams / molar mass

Multiple Choice

How many moles of silver (Ag) are in a 500 g sample?

• 1.75 moles
• 4.63 moles
• 6.02 moles
• 2.50 moles

Multiple Choice

What is the mass of 3.2 moles of silver (Ag)?

• 300.50 g
• 400.00 g
• 344.384 g
• 256.32 g

Multiple Choice

What is the mass of 1.5 moles of CaCO₃?

• 150.135 g
• 200.25 g
• 100.50 g
• 75.75 g

Multiple Choice

How many moles of CaCO₃ are in a 500 g sample?

• 2.50 moles
• 10.00 moles
• 4.99 moles
• 1.25 moles

Avogadro's number

Avogadro's number can be used to convert between the number of particles and the number of moles.

moles= particles / 6.02 x 10²³

particles= moles x 6.02 x 10²³

​Particles can be:
-atoms
-molecules
-ions

Multiple Choice

How many moles are in a sample containing 3.5 x 10²⁴ atoms?

particles / 6.02 x 10²³ = _____ moles

• 6.5 moles
• 3.0 moles
• 5.8 moles
• 4.2 moles

Multiple Choice

How many atoms are in 2.5 moles of silver (Ag)?

moles x (6.02 x 10²³) =______ atoms

• 1.505 x 10²⁴ atoms

• 2.0 x 10²⁴ atoms

• 3.01 x 10²⁴ atoms

• 1.25 x 10²³ atoms

Multiple Choice

How many molecules are in 1.25 moles of CaCO₃?

moles x (6.02 x 10²³) =______molecules

• 3.01 x 10²³ molecules

• 1.25 x 10²⁴ molecules

• 7.525 x 10²³ molecules

• 6.02 x 10²³ molecules

Multiple Choice

How many moles are in a sample containing 1.75 x 10²² molecules?

particles / 6.02 x 10²³ = _____ moles

• 0.0291 moles
• 0.0175 moles
• 0.0458 moles
• 0.0583 moles

​22.4 L in 1 mole

When Amadeo Avogadro was experimenting with gasses, he found that 1 liter of gas at STP (standard temperature and pressure which is 0^oC and 1 atmosphere)

moles = liters / 22.4 L per mole

liters= moles x 22.4 L per mole

Multiple Choice

How many moles are in a 50 L sample of carbon dioxide gas?

liter / 22.4 = _____ moles

• 2.2 moles

• 0.5 moles
• 3.0 moles
• 1.5 moles

Multiple Choice

What is the volume in liters of a 5 mole sample of oxygen gas?

moles x 22.4 = ____ liters

• 100 liters
• 50 liters
• 75 liters
• 112 liters

Let's practice!

Mixed practice problems

Multiple Choice

How many moles are in a 500L sample of nitrogen gas?

• 50 moles
• 100 moles
• 22.32 moles
• 10 moles

Multiple Choice

How many moles are there in a 100 gram sample of aluminum?

• 5.00 moles
• 1.80 moles
• 3.70 moles
• 2.50 moles

Multiple Choice

How many moles are in a sample containing 3.1 x 10²⁴ molecules of carbon dioxide?

• 2.50 moles
• 5.15 moles
• 3.10 moles
• 7.25 moles

Multiple Choice

What is the volume of a 2.35 mole sample of oxygen gas?

• 75.50 liters
• 52.72 liters
• 40.25 liters
• 30.00 liters

Multiple Choice

What is the mass of a 1.45 mole sample of CO₂?

• 78.34 g
• 45.12 g
• 50.00 g
• 63.45 g

Multiple Choice

How many molecules are in a 0.75 mole sample of silver?

• 6.022 x 10²³ molecules

• 1.5 x 10²³ molecules

• 4.5165 x 10²³ molecules

• 3.0 x 10²³ molecules