The mole

Question 1

what is a mole

Answer 1

defined as the amount of a substance that contains 6.02 X 10 (to the power of 23) entities like particles, atoms, ions, molecules, etc. of the given substance

Question 2

what is one mole of things such as atoms and molecules

Answer 2

one mole of atoms or molecules of any substance will have a mass in grams equal to the relative formula mass (Ar or Mr) for that substance

Question 3

examples of moles

Answer 3

carbon has an Ar of 12 = so one mole of carbon weighs exactly 12g
nitrogen gas has an Mr of 28 = so one mole weighs exactly 28g.

Question 4

what is the formula to find the number of moles in a given mass

Answer 4

number of moles = mass in g / Mr (of the element
(of an element /. or compound)
or compound)/

Question 5

calculate the number of moles in 90g of water (H2O)

Answer 5

Ar of O = 16. Ar of H = 1
16 + 2 = 18, Mr of H20 = 18
90/18 = 5 moles.

Question 6

rearrange the number or moles formula to make the mass the subject

Answer 6

Mass in g = number of moles X Mr

Question 7

calculate the mass of 0.20 mol of potassium bromide (KBr)

Answer 7

Ar of K = 39. Ar of Br = 80
39 + 80 = 119, Mr of KBr = 119
0.20 X 119 = 23.8g