Use the value of the Avogadro constant 6 . 02 × 10 23 mol - 1 to calculate the total number of atoms in 7 . 10 g of chlorine atoms. ( A r value: Cl = 35 . 5 ).

One mole of a substance is equal to 6 . 02 × 10 23 units of that substance (such as atoms, molecules, or ions). The number 6 . 02 × 10 23 is known as Avogadro number or Avogadro constant. The concept of the mole can be used to convert between mass and number of particles To find the number atoms in the given mass we need to calculate number of moles for given mass, we know that, Number of moles = Mass of substance Molar mass = 7 . 10 71 . 0 = 0 . 1 mol So, total number of atoms of chlorine present in 7 . 10 g 0 . 1 mol are, = 0 . 1 × 6 . 02 × 10 23 = 0 . 602 × 10 23 .

EASY

AS and A Level

IMPORTANT

Earn 100

Look at the mass spectrum of ethanoic acid.

Identify the fragment with mass-to-charge ratio of $15$ .

Important Questions on Atoms, Molecules and Stoichiometry

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 3 - Atoms, Molecules and Stoichiometry>Question>Q 4

A hydrocarbon has molecular ion peak at mass-to-charge ratio of $84$ (relative abundance $62 %$ ) and an $[M + 1]$ peak with a relative abundance of $4.1 %$ .

How many carbon atoms are in the hydrocarbon?

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 3 - Atoms, Molecules and Stoichiometry>Question>Q 5

List the ions responsible for the

M

[M + 2]

and

[M + 4]

peaks in the mass spectrum of dibromomethane.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 3 - Atoms, Molecules and Stoichiometry>Question>Q 5

What would be the mass-to-charge ratio and relative abundances of the major peaks with the highest charge-to mass ratios in the mass spectrum of chloroethane?

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 3 - Atoms, Molecules and Stoichiometry>Question>Q 5

How many peaks would you see beyond the molecular ion peak in

1, 1

-dibromoethane? What would be their mass-to-charge rations and abundances relative to the molecular ion? (Ignore peaks due to

{}^{13}C

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 3 - Atoms, Molecules and Stoichiometry>Question>Q 6

Use the

A_{r}

value of sulphur is

32.1

to calculate the amount of substance in moles in

10.7 g

of sulphur atoms.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 3 - Atoms, Molecules and Stoichiometry>Question>Q 6

Use the

A_{r}

value of sulphur is

32.1

to calculate the amount of substance in moles in

64.2 g

of sulphur molecules

(S_{8})

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 3 - Atoms, Molecules and Stoichiometry>Question>Q 6

Use these

A_{r}

values

(Fe = 55.8, N = 14.0, O = 16.0)

to calculate the amount of substance in moles in

60.45 g

of anhydrous iron(III) nitrate,

Fe {({NO}_{3})}_{3}

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 3 - Atoms, Molecules and Stoichiometry>Question>Q 6

Use the value of the Avogadro constant

(6.02 \times 10^{23} {mol}^{- 1})

to calculate the total number of atoms in

7.10 g

of chlorine atoms. (

A_{r}

value:

Cl = 35.5

Look at the mass spectrum of ethanoic acid. Identify the fragment with mass-to-charge ratio of 15.

Important Questions on Atoms, Molecules and Stoichiometry

Learn and Prepare for any exam you want !

Look at the mass spectrum of ethanoic acid.

Identify the fragment with mass-to-charge ratio of $15$ .