Chemistry Tricks Of laws of chemical combination and gas laws for NDA
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Tricks Of laws of chemical combination and gas laws for NDA

Laws of Conservation of Mass

Q 1783612547

One of the statements of Dalton's atomic theory is given below
"Compounds are formed when atoms of different elements combine in a fixed ratio"

Which of the following laws is not related to this statement?
NCERT Exemplar
(A)

Law of conservation of mass

(B)

Law of definite proportions

(C)

Law of multiple proportions

(D)

Avogadro law

Solution:

Law of conservation of mass is simply the law of indestructibility of matter during physical or
chemical changes. Avogadro law states that equal volumes of different gases contain the
same number of molecules under similar conditions of temperature and pressure.
Correct Answer is `=>` (A)
Q 1713001840

Which of the following reactions is not correct according to the law of conservation of mass?

NCERT Exemplar
(A)

`2Mg(s) + O_2(g)rightarrow 2MgO(s)`

(B)

`C_3H_8(g)rightarrowCO_2(g)+H_2O(g)`

(C)

`P_4(s)+5O_2(g)rightarrowP_4O_(10)(s)`

(D)

`CH_4(g)+2O_2(g)rightarrowCO_2(g)+2H_2O(g)`

Solution:

In this equation

`C_3H_8(g)+O_2(g)rightarrowCO_2(g)+H_2O(g)`


i.e., mass of reactants `ne` mass of products.
Hence, law of conservation of mass is not followed
Correct Answer is `=>` (B) `C_3H_8(g)rightarrowCO_2(g)+H_2O(g)`
Q 1713701649

Which of the following statements is correct about the reaction given below?

`4Fe(s) + 3O_2(g)rightarrow 2Fe_2O_3(g)`

NCERT Exemplar
(A)

Total mass of iron and oxygen in reactants= total mass of iron and oxygen in product therefore it follows law of conservation of mass

(B)

Total mass of reactants = total mass of product, therefore, law of multiple proportions is followed

(C)

Amount of `Fe_2O_ 3` can be increased by taking any one of the reactants (iron or oxygen) in excess

(D)

Amount of `Fe_2O_3` produced will decrease if the amount of any one of the reactants {iron or oxygen) is taken in excess

Solution:

According to the law of conservation of mass,
Total mass of reactants = Total mass of pmducts
Amount `Fe_2O_3`of is decided by limiting reagent
Correct Answer is `=>` (A) Total mass of iron and oxygen in reactants= total mass of iron and oxygen in product therefore it follows law of conservation of mass
Q 2837601582

Statement 1 : One molecule of ammonia always contains one atom of nitrogen and three atoms of hydrogen
Statement 2 : According to the law of conservation of mass matter can neither be created nor destroyed in a chemical reaction.

(A)

Statement-1 is true, statement-2 is true and statement-2 is correct explanation for statement-1

(B)

Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1

(C)

Statement-1 is true, statement-2 is false.

(D)

Statement 1 is false, but Statement 2 is true.

Solution:

Correct Answer is `=>` (B) Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1
Q 2827601581

Consider the following laws.
I. Law of conservation of mass
II. Law of definite proportions
III. Law of multiple proportions.
Which of these govern(s) the quantitative aspects of chemical changes?

(A)

only I

(B)

II and Ill

(C)

I and II

(D)

All of the above

Solution:

Correct Answer is `=>` (D) All of the above
Q 2857501484

Which of the following reactions is not correct according to the law of conservation of mass?

(A)

`2Mg +O_2 → 2MgO`

(B)

`C_3 +H_8+O_2 → CO_2+H_2O`

(C)

`P_4+5O_2 → P_4O_(10)`

(D)

`CH_4+2O_2 → CO_2+2H_2O`

Solution:

In equation, `underset(44 g) (C_3+H_8) +underset(32 g)(O_2) → underset(44 g) (CO_2) + underset(18) (H_2O)`

Mass of reactants `ne ` mass of products. Hence, law of conservation of mass is not followed.
Correct Answer is `=>` (B) `C_3 +H_8+O_2 → CO_2+H_2O`
Q 2837201182

Which one of the following is a correct relationship between mass and energy?

(A)

`E = hc`

(B)

`E =m/c^2`

(C)

`c = sqrt(E/m)`

(D)

`m = Ec^2`

Solution:

Einstein equation for the relationship between mass and energy is `E = mc^2` or `c = sqrt(E/m)`
Correct Answer is `=>` (C) `c = sqrt(E/m)`
Q 2877101086

If `2.0 g` of the hydrogen reacts with `16.0g` of oxygen to form `18.0 g` of water, which of the following laws is applicable ?

(A)

Law of conservation of mass

(B)

Law of constant Compositions

(C)

Law of multiple proportions

(D)

Law of reciproca proportions

Solution:

`underset(2g)(H_2) +underset(16 g) (1/2 O_2) → underset(18 g) (H_2 O) `

According to law of conservation of mass, mass of reactants = mass of products.
Correct Answer is `=>` (A) Law of conservation of mass
Q 2847101083

Which of the following statement is correct about the reaction given below? `4Fe(s) +3O_2 → 2Fe_2O_3 (g)`

(A)

Total mass of reactants = Total mass of product therefore it follows law of Conservation of mass.

(B)

Total mass of reactants = total mass of product therefore, law of multiple proportions is followed

(C)

Amount of `Fe_2O_3` can be increased by taf,ing any one of the reactants (iron or oxygen) in excess

(D)

Amount of `Fe_2O_3` produced will decrease if the amount of any one of the reactants (iron or oxygen is taken in excess

Solution:

According to the law of conservation of mass

Total mass of reactants = Total mass of products
Correct Answer is `=>` (A) Total mass of reactants = Total mass of product therefore it follows law of Conservation of mass.
Q 2846191973

Radioactive change follows the law of

(A)

conservation of mass

(B)

conservation of mass-energy

(C)

Both (a) and (b)

(D)

None of the above

Solution:

Correct Answer is `=>` (B) conservation of mass-energy
Q 2826191971

Chemical equation is balanced according to the law of

(A)

multiple proportions

(B)

reciprocal proportion

(C)

conservation of mass

(D)

definite proportion

Solution:

Correct Answer is `=>` (C) conservation of mass
Q 2816191970

Law of conservation of mass is not correct for

(A)

radioactive change

(B)

oxidation

(C)

hydrolysis

(D)

None of the above

Solution:

Correct Answer is `=>` (A) radioactive change
Q 2816091879

Which of the following law deals with mass of reactants and products during a chemical reaction?

(A)

Law of definite proportions

(B)

Law of conservation of energy

(C)

Law of conservation of mass

(D)

Law of reciprocal proportions

Solution:

Correct Answer is `=>` (C) Law of conservation of mass
Q 2817201180

Which of the following is the best example of the law of conservation of mass?

(A)

When 12 g of carbon is heated in vacuum, there is no change in mass,

(B)

Weight of platinum wire is the same before and after heating.

(C)

A sample of air increases in volume when heated at constant pressure but mass remains unchanged,

(D)

12 g of carbon combines with 32 g of oxygen to give 44 g of carbon dioxide

Solution:

Correct Answer is `=>` (A) When 12 g of carbon is heated in vacuum, there is no change in mass,

Law of Constant Composition

Q 2857201184

The law of constant proportion was proposed by

(A)

Proust

(B)

Einstein

(C)

Richter

(D)

Dalton

Solution:

Correct Answer is `=>` (A) Proust
Q 2887201187

Calcium carbonate is naturally available as limestone and can also be synthesised from quick lime. It is seen that the composition of the elements in both the natural and synthetic calcium carbonate are same. The validity of which one among the following laws is confirmed by this observation?

(A)

Law of conservation of mass

(B)

Law of definite proportions

(C)

Law of multiple proportions

(D)

Avogadro 's law

Solution:

A pure compound contains the same elements in the fixed ratio of their weights whatever its methods of preparation may be. Therefore, `CaCO_3` always contains `40 : 12 : 48` or `1 0 : 3 : 12` ratio of calcium, carbon and oxygen by weight respectively.
Correct Answer is `=>` (B) Law of definite proportions
Q 2877201186

The ratio in weight by which carbon and oxygen combine in a molecule of carbon monoxide is

(A)

`3 : 4`

(B)

`3 : 3``

(C)

`3 : 2`

(D)

`3 : 1`

Solution:

In a molecule of carbon monoxide, the ratio of carbon and oxygen by weight is `12 : 16` or `3 : 4`.
Correct Answer is `=>` (A) `3 : 4`

Law of Multiple Proportions

Q 1763001845

Which of the following statements indicates that law of multiple
proportion is being followed ?
NCERT Exemplar
(A)

Sample of carbon dioxide taken from any source will always have carbon and oxygen in the ratio 1 : 2

(B)

Carbon forms two oxides namely `CO_2` and `CO`, where masses of oxygen which combine with fixed mass of carbon are in the simple ratio 2 :1

(C)

When magnesium burns in oxygen, the amount of magnesium taken for the reaction is equal to the amount of magnesium in magnesium oxide formed

(D)

At constant temperature and pressure 200 ml of hydrogen will combine with 100 ml oxygen to produce 200 ml of water vapour

Solution:

The element, carbon, combines with oxygen to form two compounds, namely, carbon
dioxide and carbon monoxide. In `CO_2` , 12 parts by mass of carbon combine with
32 parts by mass of oxygen while in CO, 12 parts by mass of carbon combine with
16 parts by mass of oxygen.
Therefore. the masses of oxygen combine with a fixed mass of carbon (12 parts) in `CO_2`
and CO are 32 and 16 respectively. These masses of oxygen bear a simple ratio of
32 : 16 or 2 : 1 to each other.
This is an example of law of multiple proportion
Correct Answer is `=>` (B) Carbon forms two oxides namely `CO_2` and `CO`, where masses of oxygen which combine with fixed mass of carbon are in the simple ratio 2 :1
Q 1116280170

Statement-1 : In `CO` molecule `12` parts by mass of carbon combine with `16` parts by mass of oxygen and in `CO_2`, `12` parts by mass of carbon combine with `32` parts by mass of oxygen.

Statement-2 : When two elements combine separately with a fixed mass of a third element, then the ratio of their masses in which they do so is either the same or whole number multiple of the ration in which they combine with each other.

(A)

Both Statement-1 and Statement-2 are true and Statement-2 is the correct explanations of Statement-1

(B)

Both Statement-1 and Statement-2 are true and Statement-2 is not the correct explanation of Statement-1.

(C)

Statement-1 is true but Statement-2 is false.

(D)

Statement-1 is false but Statement-2 is true

Solution:

When two elements combine with each other to form two or more compounds, the masses of one of the elements which combines with fixed mass of the other, have a simple whole number ratio to one another (law of multiple proportions). Reason is the statement of law of reciprocal proportions
Correct Answer is `=>` (B) Both Statement-1 and Statement-2 are true and Statement-2 is not the correct explanation of Statement-1.
Q 1703823748

A box contains some identical red coloured balls, labelled as A, each weighing 2 g. Another box contains identical blue coloured balls, labelled as B, each weighing 5 g. Consider the combinations AB, `AB_2`, `A_2B` and `A_2B_3` and show that law of multiple proportions is applicable


NCERT Exemplar
Solution:

Mass of 8 which is combined with fixed mass of A (say 1 g) will be 2.5 g, 5 g, 1.25 g and 3.75 g. They are in the ratio 2 : 4 : 1 : 3 which is a simple whole number ratio. Hence, the law of multiple proportions is applicable
Q 2807301288

The law of multiple proportions is not illustrated by which pair of compounds

(A)

`CO` and `CO_2`

(B)

`CuO` and `Cu_2O`

(C)

`CO_2` and `H_2CO_3`

(D)

`SO_2` and `SO_3`

Solution:

Correct Answer is `=>` (C) `CO_2` and `H_2CO_3`
Q 2817401380

Which of the following compounds confirm the law of multiple proportion'?

(A)

`HgCl_2` and `Hg_2Cl_2`

(B)

`Na_2O` and `CaO`

(C)

`NaCl` and `BaCl_2`

(D)

`H_3 PO_4` and `Ca_3(PO_4 )_2`

Solution:

Correct Answer is `=>` (A) `HgCl_2` and `Hg_2Cl_2`
Q 2887301287

Which of the following compound confirm the law of multiple proportion?

(A)

`H_2O` and `H_2 O_2`

(B)

`CaO` and `Na_2 O`

(C)

`H_3PO_4` and `Ca_3(PO_1)_2`

(D)

`SO_2` and `SO_3`

Solution:

Correct Answer is `=>` (A) `H_2O` and `H_2 O_2`
Q 2877301286

Which one of the following pairs of compounds illustrate the law of multiple proportion'?

(A)

`H_2O , Na_2O`

(B)

`H_2O , H_2O_2`

(C)

`Na_2 O , BaO`

(D)

All of these

Solution:

Correct Answer is `=>` (B) `H_2O , H_2O_2`
Q 2867301285

Two elements A and B combine to form two compounds in which `a_1g` of A combines with `b_1` and `b_2 g` of B respectively. According to the law of multiple proportions

(A)

`b_1 = b_2`

(B)

`b_1` and `b_2` bear a simple wt1ole number ratio

(C)

`a_1` and `b_1` bear whole number ratio

(D)

no relation exists between `b_1` and `b_2`

Solution:

Correct Answer is `=>` (B) `b_1` and `b_2` bear a simple wt1ole number ratio
Q 2847301283

Two samples of lead oxide were separately reduced to metallic lead by heating in a current of hydrogen. The weight oflead from one oxide was half the weight of lead obtained from the other oxide. The data illustrate

(A)

law of reciprocal proportions

(B)

law of constant proportions

(C)

Law of multiple proportions

(D)

law of equivalent proportions

Solution:

Correct Answer is `=>` (C) Law of multiple proportions
Q 2827301281

Different propottions of oxygen in the various oxides of nitrogen prove the law of

(A)

equivalent proportion

(B)

multiple proportions

(C)

constant proportions

(D)

conservation of matter

Solution:

Correct Answer is `=>` (B) multiple proportions
Q 2817201189

The law of multiple proportions was proposed by

(A)

Lavoisier

(B)

Dalton

(C)

Proust

(D)

Gay-Lussac

Solution:

Correct Answer is `=>` (B) Dalton
Q 2807201188

Two different oxides of a metal contain 20% and 27'% oxygen by weight. This is an accordance with the law of

(A)

conservation of mass

(B)

constant composition

(C)

multiple proportion

(D)

reciprocal proportion

Solution:

Correct Answer is `=>` (C) multiple proportion

Law of Reciprocal Proportions

Q 2847401383

`8 g` of oxygen combine with `1 g` of hydrogen and `20 g` of calcium therefore, when calcium combines with hydrogen it must combine in the ratio of `20 : 1`. This statement confirms to the law of

(A)

multiple proportions

(B)

reciprocal proportions

(C)

definite proportions

(D)

gaseous volume

Solution:

Correct Answer is `=>` (B) reciprocal proportions
Q 2837401382

Hydrogen, sulphur and oxygen gives `H_2S , SO_2` and `H_2O.` This is according to the law of

(A)

constant proportions

(B)

multiple proportions

(C)

reciprocal proportions

(D)

conservation of mass

Solution:

Correct Answer is `=>` (C) reciprocal proportions

Gay-Lussac's Law of Combining Volumes

Q 2817501480

In the reaction, `N_2 +3H_2 → 2NH_3` ratio by volume of `N_2 , H_2` and `NH_3` is `1 : 3 : 2.` This suggested law of

(A)

definite proportions

(B)

multiple proportions

(C)

reciprocal proportions

(D)

combining volume

Solution:

`underset ( 1 vol )(N_2) + underset(3 vol)(3H_2) → underset(2 vol) (2 NH_3)`

According to law of combining volumes; when gases react together, they always do so in volumes which bear a simple ratio to one another and to the volume of the products.
Correct Answer is `=>` (D) combining volume
Q 2877401386

According to which one of the following laws it is indicated that when two or more gases react with one another, their volume bear a
simple ratio?

(A)

Law of mass action

(B)

law of multiple proportions

(C)

law of reciprocal proportions

(D)

Law of combining volumes

Solution:

Correct Answer is `=>` (D) Law of combining volumes
Q 2867401385

Law of combining 'volumes was given by

(A)

Dalton

(B)

Tswett

(C)

Gay-Lussac

(D)

Einstein

Solution:

Correct Answer is `=>` (C) Gay-Lussac

Gas Laws

Q 1502178938

Gay Lussac's law of gaseous volume is derived from
BITSAT 2013
(A)

Law of definite proportions

(B)

Law of multiple proportions

(C)

Law of reciprocal proportions

(D)

experimental observation

Solution:

Gay Lussac's law of gaseous volume is derived from experimental observation. According to this law, at constant volume, pressure of a given mass of a gas varies directly with the temperature.
Correct Answer is `=>` (D) experimental observation
Q 2559134914

If `2` moles of an ideal gas at `546 K` occupy volume `44.8 L`, then pressure must be
BCECE Mains 2015
(A)

`2` atm

(B)

`3` atm

(C)

`4` atm

(D)

`1` atm

Solution:

From gas equation, `pV = nRT`

Given, that, `V = 44.8 L`

`n = 2`

`R = 0.0821 L` atm/mol/K

`T = 546 K`

`P = (2 xx 0.0821 xx 546)/(44.8) = 2` atm
Correct Answer is `=>` (A) `2` atm
Q 2817601580

Consider the following statements,
I. The ideal gas consists of a large number of small particles called molecules,
II. Under the same conditions of temperature and pressure equal volumes of gases contain the same number of molecules.
III. Volume of a definite quantity of gas at constant pressure is directly proportional to absolute temperature.

Which of the above statements is Avogadro's hypothesis?

(A)

only I

(B)

only II

(C)

I and II only

(D)

None of these

Solution:

Correct Answer is `=>` (B) only II
Q 2817501489

Ideal gas equation is the combination of
I. Boyle's law
II. Charles' law
III. Avogadro law
IV. Dalton's law of partial pressure

(A)

I and II

(B)

I, II and lll

(C)

II and III

(D)

I, Ill and lV

Solution:

Correct Answer is `=>` (B) I, II and lll
Q 2867501485

Pressure of a gas increases due to increase of its temperature because at higher temperature

(A)

gas molecules repel each other

(B)

potential energy of the gas molecules is higher

(C)

kinetic energies of the gas molecules are higher

(D)

gas molecules attract each other

Solution:

Correct Answer is `=>` (C) kinetic energies of the gas molecules are higher
Q 2847501483

Real gas will approach the behaviour of ideal gas at

(A)

low temperature and high pressure

(B)

high temperature and low pressure

(C)

low temperature and low pressure

(D)

high temperature and high pressure

Solution:

Correct Answer is `=>` (B) high temperature and low pressure
Q 2837501482

Equal masses of oxygen, hydrogen and methane are kept under identical conditions. The ratio of the volumes of gases will be

(A)

`1 : 1 : 1`

(B)

`1 : 16 : 2`

(C)

`2 : 16 : 1`

(D)

`1 : 4 : 1`

Solution:

`underset(O_2) (text(Oxygen)) \ \ \ \ underset(H_2) ( text(Hydrogen)) \ \ \ \ underset(CH_4) (text(Methane))`

Number of moles

`1/32 = 0.031 , 1/2 = 0.5 ; 1/16 = 0.0625`

Simple ratio ` 1 \ \ \ \ \6 \ \ \ \ \ \ \ \ 2`

Equal number of moles of gases occupy equal volumes under similar conditions of temperature and pressure, therefore
the ratio of the volumes of gases will be `1 : 16 : 2.`
Correct Answer is `=>` (B) `1 : 16 : 2`
Q 2058356204

Match the following gas laws with the equation representing them.








Column IColumn II
(A) Boyle's law (1) `V prop n` at constant T and p
(B) Charle's law (2) `P_(Total) = p_1 + p_2 + p_3` + ... at constant T, V
(C) Dalton's law (3) `(pV)/T` = constant
(D) Avogadro's law (4) `V prop T` at constant n and p
(5) `p prop 1/V` constant n and T

NCERT Exemplar
Solution:

`A. -> (5) B. -> (4) C. -> (2) D.-> (1)`

A Boyle's law, `p prop 1/V` at constant T and n.

B. Charle's law, `V prop T` at constant p and n.

C. Dalton's law, `P_text(Total) = p_1 + p_2 + p_3 +` ... at constant T, V

D. Avogadro's law, `V prop n` at constant T and p.
Q 1775634566

As the temperature increases, average kinetic energy of molecules
increases. What would be the effect of increase of temperature on
pressure provided the volume is constant?
NCERT Exemplar
(A)

Increases

(B)

Increases

(C)

Remains same

(D)

Becomes half

Solution:

As the temperature increases, average kinetic energy of molecules increases. From
Gay-Lussac's law, at constant volume, as the temperature is increased, pressure
increases
Correct Answer is `=>` (A) Increases
Q 1641823723

Which of the following statements is not
correct?
GGSIPU 2015
(A)

At constant volume, the pressure of a certain amount of gas increases with increasing temperature

(B)

At constant temperature, the pressure of a certain amount of gas increases with increasing volume

(C)

At constant pressure, the volume of a certain amount of gas increases with increasing volume

(D)

In dealing with gas laws, the most convenient scale of temperature to use is the kelvin temperature scale

Solution:

According to Boyle's law, "At a given temperature,
the volume of a given mass of a gas is inversely
proportional to its pressure".

At constant temperature `p ∝ 1/V` (according to Boyle's law)

`:.` At constant temperature, the pressure of a
certain amount of gas increase with decreasing
volume.
Correct Answer is `=>` (B) At constant temperature, the pressure of a certain amount of gas increases with increasing volume
Q 2887501487

With regard to the gaseous state of matter which of the following statements are correct'?

(A)

Complete order of molecules

(B)

Complete clisorcler ol molecules

(C)

Random motion ot molecules

(D)

Both (b) and (c)

Solution:

Correct Answer is `=>` (D) Both (b) and (c)
Q 2877501486

A pressure cooker works on the principle of

(A)

elevation of boiling point of water by the application of pressure

(B)

making lhe food-grains softer by the application of pressure

(C)

making the food grains softer by the application of pressure and temperature

(D)

keeping the food grains inside steam for a longer time

Solution:

Correct Answer is `=>` (A) elevation of boiling point of water by the application of pressure
Q 2857401384

Equal volumes of all gases under same temperature and pressure contain equal number of molecules according to

(A)

Avogadro's law

(B)

Charles law

(C)

Boyle's law

(D)

Graham's law

Solution:

Correct Answer is `=>` (A) Avogadro's law
Q 2847601583

Statement 1 : On increasing the temperature of an ideal gas 10°C at constant volume, the pressure increases by 10%.
Statement 2 : At a constant volume, the pressure of a given mass of a gas is directly proportional to its absolute temperature.

(A)

Statement-1 is true, statement-2 is true and statement-2 is correct explanation for statement-1

(B)

Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1

(C)

Statement-1 is true, statement-2 is false.

(D)

Statement 1 is false, but Statement 2 is true.

Solution:

Correct Answer is `=>` (A) Statement-1 is true, statement-2 is true and statement-2 is correct explanation for statement-1
 
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