The Mole

Question 0

Why do we measure things in moles?

Answer 0

Because these things/particles are so tiny, that we need a number

Question 1

What is a mole?

Answer 1

It is a unit of measurement of the amount of substance that contains the same number of particles as there are atoms in 12 g of C12 (6.02 x 10^23).
Unit: mol

Question 3

Molar mass (M)

Answer 3

The mass of one mole of an element or compound.
Of an element: relative atomic mass
Of a compound: relative molecular/formula mass
Unit: g/mol OR g mol-1

Question 4

Avagadro’s number (NA)

Answer 4

The number of atoms, molecules, or ions in 12 g of C12 = 6.02 x 10^23

Unit: particles/mol OR particles mol-1

Question 5

Mass (m)

Answer 5

Weight of substance in grams.

Unit: g

Question 6

What are the 3 steps for calculations equations?

Answer 6

1. Determine what information you have or what information we can use.
2. Determine what information we need to calculate the equation.
3. Arrange equation using appropriate conversion.

Question 7

Percentage Composition

Answer 7

The % that each element contributes to the overall mass of a compound.

Question 8

Percentage composition formula.

Answer 8

% of x(element)= mass of x in 1 mol (Molar Mass) x 100

molar Mass of a compound 1

Question 9

Empirical Formula

Answer 9

The formula of a compound that gives the simplest whole number ratio of atoms or ions in the compound.

Question 10

Molecular Formula

Answer 10

The formula of a compound that gives the actual number of atoms of each element present in a molecule of a compound.

Question 11

Steps involved in finding the empirical formula for percentage composition.

Answer 11

1) Write down the symbols of the elements present.
2) Assume the mass of the sample is 100g and all percentage becomes grams.
3) Convert masses to moles by using the mole formula- n=m/M
4) Find the simplest whole number ratio of the atoms by dividing all numbers of moles by the smallest number of moles.
5) If necessary, multiply by a factor to get a whole number.

Question 12

The molecular formula can by determined when the following information is given…

Answer 12

Molar mass of the molecular formula

Empirical formula is known or can be worked out.

Question 13

To work out the molecular formula, you use the equation.

Answer 13

Molecular formula= whole no. ratio x empirical formula

Question 14

What formula is used to calculate the number of moles of an element or compound?

Answer 14

n=m/M

Question 15

What other formula is used to calculate the number of moles?

Answer 15

n= no. of particles

6.02 x 10^23

Question 16

Particles

Answer 16

Either molecules, atoms, ions, electrons.