Stoichiometry revision

Stoichiometry Review

How to find Molar Mass of a substance

Molar Mass is the mass in grams of one mole of a substance.

1. Find the atomic mass of each element from the Periodic table.

   (ex: C₆H₁₂O₆ has C, H and O)

2. Multiply the mass of each element by the number of atoms in that compound. (ex: 12.01 x 6 = 72.06 g/mol)

3. Add the molar masses of​ each element in the compound together.

   (ex: C₆H₁₂O₆, 72.06 + 12.08 + 95.99 = 180.14 g /mol)​

Multiple Choice

What is the molar mass of fluorine gas?

• 18.998 g/mol
• 38 g/mol
• 9 g/mol
• 18 g/mol

How to use Molar Mass to convert to Moles

Molar Mass is the mass in grams of one mole of a substance.

1. Find the molar mass of a substance.

​ (ex: 1 mole of HCl = 36.46 g of HCl)

3. If we are given the mass, we compare to our molar mass.

   The formula: number of moles = mass / molar mass

   (ex: 9 g of HCl is used. 9 g / 36.46 gmol^-1 = 0.25 mol of HCl.)

Multiple Choice

Find the mass of 5.82 mol of MgCl₂. Round to the nearest tenth.

• 552.9 g

• 436.8 g

• 55.2 g

• 555.9 g

Multiple Choice

Find the mass of 3.8 mol of H₂O. Round to the nearest tenth.

• 57.9 g

• 54.8 g

• 68.4 g

• 62.3 g

Multiple Choice

Determine the number of moles of AlNO₃ that are in 264 g of the compound.

• 2.97 mol

• 3.45 mol

• 2.73 mol

• 1.86 mol

What is stoichiometry?

What is it?

STOICHIOMETRY is about PROPORTIONS in a chemical reaction.


A method to calculate the quantity of reactants.​

-or​-

A method to calculate the quantity of products.

Quantity can be: moles, mass, concentration, volume.

Steps in Stoichiometry

You will need to:​

1. Balance the chemical equation.

2. Write the information from the question above the chemical equation.

3. Write the number of moles (coefficients) below the equation.

4. Set up your proportion.

5. Cross-multiply and solve for x.​

Draw

Balance this equation. Show your work and complete answer.

Draw

If 5 grams of H₂0 were produced in this reaction, how many grams of C₃H₈ were combusted? Show your work.

Multiple Choice

What is the molar mass of C₆H₁₂O₆?

• 180.18
• 180.12
• 180.24
• 180.06

Multiple Choice

WO₃ + H₂ --> W + H₂O
What coefficient goes in front of H₂?

• 1
• 2
• 3
• 4

Multiple Choice

What is the first thing you must do to solve a stoichiometry problem?

• Make sure the chemical reaction is Balanced

• Panic

• Make sure the Equation is Unbalanced

• Multiple by Avogadro's Number

Multiple Choice

How many moles of H₂ are needed to react with 2 moles of N₂ according to the reaction?

1 N₂ + 3 H₂ → 2 NH₃

• 6

• 2

• 3

• 1

Multiple Choice

If 12.00 moles of NaClO₃ react, how many moles of O₂ will be produced according to the reaction?

2 NaClO₃ → 2 NaCl + 3 O₂

• 12 moles of O₂

• 18 moles of O₂

• 9 moles of O₂

• 6 moles of O₂

Multiple Choice

1 Cl₂ + 2 KBr → 1 Br₂ + 2 KCl

How many GRAMS of KCl can be produced from 356 g of KBr?

• 749 g

• 223 g

• 479 g

• 814 g

Multiple Choice

Using the following equation:
Fe₂O₃(s) + 3H₂(g) → 2Fe(s) + 3H₂O(l)
How many moles of iron can be made from  6 moles H₂? 

• 4 moles Fe
• 6 moles Fe
• 9 moles Fe
• 2 moles Fe