Quantitative Chemistry: Relative Formula Mass (DONE)

Question 1

What is the relative formula mass? (Mr)

Answer 1

The relative formula mass of a compound is the sum of the relative atomic masses of the atoms in the numbers shown in the formula.

Question 2

What is the unit of relative formula mass?

Answer 2

This was a trick question. Relative formula mass doesn’t have no units.

Question 3

Are you allowed to use big numbers when calculating the relative formula mass?

example: 2O↓3

Answer 3

No, you cannot use the big 2 to help you calculate the relative formula mass. But you can still calculate the relative formula mass just don’t use the 2.

Question 4

What is relative atomic mass? (Ar)

Answer 4

The relative atomic mass of an element is the average mass of the isotopes of that element to take into account the abundance of each isotope.

Question 5

Calculate the relative formula mass of:

2CH↓4

A ↓ r C = 12
A ↓ r H = 1

Answer 5

1 x 12
4 x 1

12 + 4 = 16

Mr = 16

(the two doesn’t change anything, two just means we have two molecules of methane)

Question 6

Calculate the relative formula mass of:

Mg (OH)↓2

A ↓ r Mg = 24
A ↓ r O = 16
A ↓ r H = 1

Answer 6

1 x 24 = 24
2 x 16 = 32
2 x 1 = 2

24 + 32 + 2 = 58

Mr = 58