Complete the table given below. Element Atomic mass Molecular mass Atomicity number Chlorine 35.5 71 - Ozone - 48 3 Sulphur 32 - 8 Nitrogen 14 - 2

Element Atomic mass Molecular mass Atomicity number Chlorine 35.5 71 2 Atomicity = Molecular mass Atomic mass = 71 35 . 5 = 2 Chlorine is a diatomic molecule. Atomicity can be defined as the total number of atoms that compose a molecule. Simply put, it is the number of atoms present in a molecule. Element Atomic mass Molecular mass Atomicity number Ozone 16 48 3 Atomic mass = Molecular mass Atomicity number = 48 3 = 16 Ozone is a triatomic molecule. Its molecular formula is O 3 . The mass of an atom of a chemical element expressed in atomic mass units. It is approximately equivalent to the number of protons and neutrons in the atom. Element Atomic mass Molecular mass Atomicity number Sulphur 32 256 8 Molecular mass = Atomic mass × Atomicity number = 32 × 8 = 256 Sulphur is a polyatomic molecule. Its molecular formula is S 8 . Element Atomic mass Molecular mass Atomicity number Nitrogen 14 28 2 Molecular mass = Atomic mass × Atomicity number = 14 × 2 = 28 Nitrogen is a diatomic molecule. Its molecular formula is N 2 . Molecular mass ( m ) is the mass of a given molecule: it is measured in daltons (Da or u)

Ethane burns in oxygen to form CO 2 and H 2 O according to the equation 2 C 2 H 6 + 7 O 2 → 4 CO 2 + 6 H 2 O . If 1250 cc of oxygen is burnt with 300 cc of ethane. Calculate the volume of unused O 2 .

2 C 2 H 6 + 7 O 2 → 4 CO 2 + 6 H 2 O In the balance equation given, the number of moles of oxygen is 3 . 5 times the number of moles of ethane. Hence, the volume of oxygen will also be thrice the amount of ethane. To burn 300 cc of ethane, the amount of oxygen needed = 3 . 5 × 300 = 1050 cc The amount of oxygen burnt with 300 cc of ethane in the given question = 1250 cc Hence, the amount of unused oxygen 1250 - 1050 cc = 200 cc of oxygen.

Copper sulphate solution reacts with sodium hydroxide solution to form a precipitate of copper hydroxide according to the equation: 2 NaOH + CuSO 4 → Na 2 SO 4 + Cu ( OH ) 2 ↓ i) What mass of copper hydroxide is precipitated by using 200 gm of sodium hydroxide? [ H = 1 , O = 16 , Na = 23 , S = 32 , Cu = 64 ] (ii) What is the colour of the precipitate formed?

(i) 2 NaOH + CuSO 4 → Na 2 SO 4 + Cu ( OH ) 2 ↓ Molecular mass of sodium hydroxide = 2 ( 23 + 16 + 1 ) = 80 g Molecular mass of copper hydroxide = 64 + 32 + 2 = 98 g 98 g of Cu ( OH ) 2 is precipitated by using 80 g of NaOH . x g of Cu ( OH ) 2 is precipitated by using 200 g of NaOH . x = 98 80 × 200 g = 245 g of Cu ( OH ) 2 (ii) A light blue precipitate of copper hydroxide will be formed.

Nitroglycerine is used as an explosive. The equation for the explosive reaction is: 4 C 3 H 5 ( NO 3 ) 3 → 12 CO 2 + 10 H 2 O + 6 N 2 + O 2 ( l ) ( g ) ( l ) ( g ) ( g ) Atomic mass of C = 12, H = 1, N = 14, O = 16) How many moles does the equation show for gas molecules produced?

The number of moles of nitroglycerine is 4. The number of moles of gas produced by 4 moles of nitroglycerin are- The number of gas molecules = 12 CO 2 + 6 N 2 + O 2 = 12 + 6 + 1 = 19 moles The mole is the base unit of the amount of substance in the International Unit of System of Units (SI). It is defined as exactly 6 . 022 × 10 23 elementary particles, which may be atoms, molecules, ions, or electrons.

Aluminium carbide reacts with water according to the following equation: Al 4 C 3 s + 12 H 2 O l → 4 Al OH 3 aq + 3 CH 4 g What volume of methane at s.t.p. is obtained from 12 g of aluminium carbide? [Relative molecular weight of Al 4 C 3 = 144 , Al OH 3 = 78 ]

Al 4 C 3 s + 12 H 2 O l → 4 Al OH 3 aq + 3 CH 4 g 144 g of Al 4 C 3 gives 3 × 12 + 4 × 1 = 48 g of methane. Therefore, 12 g of Al 4 C 3 gives = 12 × 48 144 = 4 g of CH 4 We know that 1 mole of any gas at STP occupies a volume of 22 . 4 L Therefore, the volume occupied by 4 g of CH 4 = 4 16 × 22 . 4 = 5 . 6 L

Nitroglycerine is used as an explosive. The equation for the explosive reaction is: 4 C 3 H 5 ( NO 3 ) 3 → 12 CO 2 + 10 H 2 O + 6 N 2 + O 2 (Atomic mass of C = 12, H = 1, N = 14, O = 16) How many moles of gas molecules are obtained from 1 mole of nitroglycerine.

4 moles of nitroglycerine give 19 moles of gas molecules. 1 mole of nitroglycerine gives = 19 4 = 4 . 75 moles Hence, 1 mole of nitroglycerine produces 4.75 moles of gas. The mole is the base unit of the amount of substance in the International Unit of System of Units (SI). It is defined as exactly 6 . 022 × 10 23 elementary particles, which may be atoms, molecules, ions, or electrons.

Nitroglycerine is used as an explosive. The equation for the explosive reaction is: 4 C 3 H 5 ( NO 3 ) 3 → 12 CO 2 + 10 H 2 O + 6 N 2 + O 2 ( l ) ( g ) ( l ) ( g ) ( g ) (Atomic mass of C = 12, H = 1, N = 14, O = 16) How many moles does the equation show for nitroglycerine?

4 C 3 H 5 ( NO 3 ) 3 → 12 CO 2 + 10 H 2 O + 6 N 2 + O 2 The number of moles is shown by nitroglycerine = 4 moles . The mole is the base unit of the amount of substance in the International Unit of System of Units (SI). It is defined as exactly 6 . 022 × 10 23 elementary particles, which may be atoms, molecules, ions, or electrons.

Aluminium carbide reacts with water according to the following equation: Al 4 C 3 s + 12 H 2 O l → 4 Al OH 3 aq + 3 CH 4 g . What mass of aluminium hydroxide is formed from 12 g of aluminium carbide?

Al 4 C 3 s + 12 H 2 O l → 4 Al OH 3 aq + 3 CH 4 g Atomic masses of the elements are: Al = 27 ; C = 12 ; O = 16 ; H = 1 From the above reaction, molecular mass of Al 4 C 3 = 144 g / mol Molecular mass of Al OH 3 = 78 g / mol Amount of aluminium hydroxide formed from 144 g of aluminium carbide = 4 27 × 1 + ( 12 + 1 ) × 3 = 312 g So, the amount of aluminium hydroxide formed from 12 g of aluminium carbide = 4 × 78 × 12 144 = 26 g

Nitroglycerine is used as an explosive. The equation for the explosive reaction is: 4 C 3 H 5 ( NO 3 ) 3 → 12 CO 2 + 10 H 2 O + 6 N 2 + O 2 (Atomic mass of C = 12, H = 1, N = 14, O = 16) What is the mass of 1 mole of glycerine?

Mass of 1 mole of nitroglycerine [ C 3 H 5 ( N O 3 ) 3 ] = C ( 3 × 12 ) + H ( 1 × 5 ) + N ( 3 × 14 ) + O ( 9 × 16 ) = C ( 36 ) + H ( 5 ) + N ( 42 ) + O ( 144 ) = 227 g Mass of 1 mole of nitroglycerine is 227g. The total sum of the masses of the atoms of elements present in a molecule is termed as molecular mass.

EASY

Earn 100

Define molecular mass.

Important Questions on Atoms and Molecules

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Find how many moles of atoms are there in:

14 g of lithium.

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Complete the table given below.

Element	Atomic mass	Molecular mass	Atomicity number
Chlorine	35.5	71	-
Ozone	-	48	3
Sulphur	32	-	8
Nitrogen	14	-	2

HARD

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Calculate the amount of each reactant required to produce $750 ml$ of carbon dioxide, when two volumes of carbon monoxide combine with one volume of oxygen to produce two volumes of carbon dioxide.

$2 CO + O_{2} \to 2 {CO}_{2}$

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Find how many moles of atoms are there in:

32 g of sulphur.

HARD

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Ethane burns in oxygen to form ${CO}_{2}$ and $H_{2} O$ according to the equation $2 C_{2} H_{6} + 7 O_{2} \to 4 {CO}_{2} + 6 H_{2} O$ . If $1250 cc$ of oxygen is burnt with $300 cc$ of ethane. Calculate the volume of unused $O_{2}$ .

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Find how many moles of atoms are there in:

7 g of nitrogen.

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Find how many moles of atoms are there in:

4.6 g of sodium.

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Copper sulphate solution reacts with sodium hydroxide solution to form a precipitate of copper hydroxide according to the equation:

$2 NaOH + {CuSO}_{4} \to {Na}_{2} {SO}_{4} + Cu {(OH)}_{2} ↓$

i) What mass of copper hydroxide is precipitated by using $200 gm$ of sodium hydroxide?

$[H = 1, O = 16, Na = 23, S = 32, Cu = 64]$

(ii) What is the colour of the precipitate formed?

EASY

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

What is the molar mass of Nitric acid?

[H = 1 u, N = 14 u, O = 16 u]

HARD

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Substances having an equivalent number of molecules as in

9 g

of water:

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Nitroglycerine is used as an explosive. The equation for the explosive reaction is:

$4 C_{3} H_{5} {({NO}_{3})}_{3} \overset{}{\to} 12 {CO}_{2} + 10 H_{2} O + 6 N_{2} + O_{2} (l) (g) (l) (g) (g)$

Atomic mass of C = 12, H = 1, N = 14, O = 16)

How many moles does the equation show for gas molecules produced?

HARD

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Aluminium carbide reacts with water according to the following equation: ${Al}_{4} C_{3} (s) + 12 H_{2} O (l) \to 4 Al {(OH)}_{3} (aq) + 3 {CH}_{4} (g)$

What volume of methane at s.t.p. is obtained from $12 g$ of aluminium carbide? [Relative molecular weight of ${Al}_{4} C_{3} = 144, Al {(OH)}_{3} = 78$ ]

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Nitroglycerine is used as an explosive. The equation for the explosive reaction is:

$4 C_{3} H_{5} {({NO}_{3})}_{3} \overset{}{\to} 12 {CO}_{2} + 10 H_{2} O + 6 N_{2} + O_{2}$

(Atomic mass of C = 12, H = 1, N = 14, O = 16)

How many moles of gas molecules are obtained from 1 mole of nitroglycerine.

MEDIUM

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Find how many moles of atoms are there in:

40 g of calcium.

EASY

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Nitroglycerine is used as an explosive. The equation for the explosive reaction is:

$4 C_{3} H_{5} {({NO}_{3})}_{3} \overset{}{\to} 12 {CO}_{2} + 10 H_{2} O + 6 N_{2} + O_{2} (l) (g) (l) (g) (g)$

(Atomic mass of C = 12, H = 1, N = 14, O = 16)

How many moles does the equation show for nitroglycerine?

EASY

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

The balanced chemical equation for the formation of ammonia gas by the reaction between nitrogen gas and hydrogen gas is given.

$N_{2} + 3 H_{2} \to 2 {NH}_{3}$

How many moles of ammonia are formed when 6 moles of $N_{2}$ reacts with 6 moles of $H_{2}$ ?

EASY

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

The number of moles in $400 g$ ${CaCO}_{3}$ is _____ moles.

[Hint: Gram atomic masses: $Ca = 40 g, C = 12 g, O = 16 g$ ]

EASY

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Calculate the weight of

10^{22}

atoms of carbon. [

C = 12

, Avogadro’s No.=

6 \times 10^{23}

]

HARD

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Aluminium carbide reacts with water according to the following equation: ${Al}_{4} C_{3} (s) + 12 H_{2} O (l) \to 4 Al {(OH)}_{3} (aq) + 3 {CH}_{4} (g)$ .

What mass of aluminium hydroxide is formed from $12 g$ of aluminium carbide?

EASY

Science>Chemistry>Atoms and Molecules>Molecular Mass and Mole Concept

Nitroglycerine is used as an explosive. The equation for the explosive reaction is:

$4 C_{3} H_{5} {({NO}_{3})}_{3} \overset{}{\to} 12 {CO}_{2} + 10 H_{2} O + 6 N_{2} + O_{2}$

(Atomic mass of C = 12, H = 1, N = 14, O = 16)

What is the mass of 1 mole of glycerine?

Define molecular mass.

Important Questions on Atoms and Molecules

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