Chemical formulae, equations and calculations (Moles)

Question 1

atomic number

Answer 1

the number of protons in the nucleus of an atom

Question 2

atomic mass

Answer 2

the number of protons and neutrons in the nucleus of an atom

Question 2

isotopes

Answer 2

atoms of the same element which have the same number of protons but a different number of neutrons

Question 2

what is the relative molecular mass (RMM) of CO2?

Answer 2

C = 12

0= 16

12 + (16 x 2)

=44

Question 3

what is magnesium’s atomic mass in comparison to carbon

Answer 3

C : Mg

12 : 24

1 : 2

you divide by the smallest number or smallest factor of the two numbers

Question 4

what is the relative molecular mass (RMM) of Ca (OH)2

Answer 4

Ca = 40

O = 16

H = 1

Ca + (O x 2) + (H x 2)

=74

Question 5

Calulate the relative molecular mass (Mr) of NH4NO3

Answer 5

N = 14

H = 1

O = 16

14 + (1 x 4) +14 + (16 x 3)

= 80

Question 5

Caluculate the number of moles in 0.26g of Ca0

Answer 5

m = 0.26

Mr = 40 +16 = 56

n = 0.26 ÷ 56

= 0.0046 mol

Question 6

Find the mass of 3.2 moles of SO2

Answer 6

mass = moles x Mr

3.2 x (32+(16x2))

=3.2 x 64

= 204.8

Question 7

calculate the relative atomic mass of the isotope chlorine where:

25% 37_Cl

75% 35_Cl

Answer 7

25 ÷ 100 x 37 = 9.25

75 ÷ 100 x 35 = 26.25

9.25 + 26.25 = 35.5

= 35.5

Question 8

how many moles are in 1.8g of H2O?

Answer 8

moles = mass ÷ Mr

mols = 1.8g ÷ 18

=0.1 mol