U3

Question 1

Define the Mole as the SI base unit for the amount of a substance

Answer 1

Mole is the SI base unit for the amount of a substance. It is the mount of entities in 12.00g of Carbon-12.

Question 2

What is Avogadro’s Constant? What is each entity called?

Answer 2

6.02 x 10^23
Atoms / Ions - For Single Atoms or Ions
Molecules - Covalent Compounds
Formula Units - Ionic Compounds

Question 3

What is molar mass?

Answer 3

Molar mass is how many grams of a substance is required to make up one mol of the substance

Question 4

How to find molecular mass?

Answer 4

Add the molar masses of each atom in the molecule

Question 5

What is the triangle for mol calculations?

Answer 5

[padding] ——– m (mass)
______________________________________
M (molar mass) | n (# of mols)

Question 6

What is the triangle for particle calculations?

Answer 6

[padding] N (# of particles)
_____________________________________
n (# of mols) | NA (Avogadro’s #)

Question 7

Define and calculate percentage composition (triangle)

Answer 7

The percentage, by mass, of each element in the compound

    Mass of Element × 100 ------------------------------------------    % Composition | Total Mass

Question 8

What is the Law of Definite Proportions?

Answer 8

“The elements in a chemical compound are always present in the same proportions by mass”
Does not imply that elements in compounds are always present in the same relative amounts.

Question 9

Empirical vs Molecular Formula

Answer 9

Empirical formula is the most simplified version of the molecular formula
Molecular formula is the actual formula for the compound

Question 10

How to find empirical formula?

Answer 10

Percentage –> Mass
Mass –> Mols
Divide all mols by smallest
Round if close, multiply if not
–> Mols

Percent to Mass, Mass to Mole, Divide by Small, Multiply ’til Whole

Question 11

How to find molecular formula from empirical formula?

Answer 11

Molar Mass of Compound
—————————————= Multiplier
Molar Mass of Empirical Formula

Multiply empirical formula subscripts by multiplier to get molecular formula

Question 12

How to find mass percent of water in a hydrate?

Answer 12

Water mass
————————— x 100 = Mass Percent
Total Sample Mass

Question 13

How to find formula of a hydrate?

Answer 13

Same rules for finding empirical formula.
Percentage –> Mass
Mass –> Mols
Divide all mols by smallest
Round if close, multiply if not
–> Mols

Non water should always have coefficient of 1

Question 14

How do you calculate the amount or mass of product formed from a given mass of reactant?

How do you calculate the amount or mass of reactant needed to produce a specified mass of product?

Answer 14

1. Mass –> Mols
   Find mols of product using the mol ratio
   (reactant mols x product coefficient / reactant coefficient)
   Mols –> Mass
2. Switch around reactant and product

Question 15

How to find limiting reactant?

Answer 15

Mass –> Mols
Mol ratio –> Mols of missing data
Limiting reactant produces smaller amount of mols in missing data

Question 16

What is theoretical and actual yield?

Answer 16

Theoretical yield is the amount of product expected to be produced from the equation
Actual yield is the actual amount of product produced

Question 17

What is the triangle for calculating yields?

Answer 17

[pad] – Actual Yield × 100
—————————————-
Theoretical Yield | % Yield