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.

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

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.

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Chlorofluorocarbons (or CFCs) are chemicals that destroy the ozone in the atmosphere. A common CFC has a chemical formula ${CCl}_{2} F_{2}$ . Using the table below, what is the relative formula mass of ${CCl}_{2} F_{2}$ ?

Chemical symbol Element Relative atomic mass

$C$ Carbon $12$

$Cl$ Chlorine $35.5$

$F$ Fluorine $19$

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Important Questions on Atoms and Molecules

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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 ${Al}_{4} C_{3} = 144, Al {(OH)}_{3} = 78$ ]

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Science>Chemistry>Atoms and Molecules>Molecular Mass

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Science>Chemistry>Atoms and Molecules>Molecular Mass

The contribution to the total current in a semiconductor, due to electrons and holes are

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List - I List-II
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Consider an ionic solid

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(Z)

, whose unit cell is constructed from the unit cell of

MX

, following the sequential instructions given below. Neglect the charge balance.

(i)

Remove all the anions

(X)

, except the central one.

(ii)

Replace all the face centered cations

(M)

, by anions

(X)

(iii)

Remove all the corner cations

(M)

(iv)

Replace the central anion

(X)

, with cation

(M)

.

The value of

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Science>Chemistry>Atoms and Molecules>Molecular Mass

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?

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Science>Chemistry>Atoms and Molecules>Molecular Mass

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?

Chemical symbol	Element	Relative atomic mass
$C$	Carbon	$12$
$Cl$	Chlorine	$35.5$
$F$	Fluorine	$19$

Chlorofluorocarbons (or CFCs) are chemicals that destroy the ozone in the atmosphere. A common CFC has a chemical formula CCl2F2. Using the table below, what is the relative formula mass of CCl2F2? Chemical symbol Element Relative atomic mass C Carbon 12 Cl Chlorine 35.5 F Fluorine 19

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