Some Basic Concepts of Chemistry Set-1

Question 1

What will be the molarity of a solution, which contains $5.85	ext{g of } 	ext{NaCl}(	ext{s}) 	ext{ per } 500	ext{mL}$?

Accepted Answer

$0.2	ext{ mol L}^{-1}$

Answer

$4	ext{ mol L}^{-1}$

Answer

$20	ext{ mol L}^{-1}$

Answer

$2	ext{ mol L}^{-1}$

Question 2

Zinc sulphate contains $22.65\%$ zinc and $43.9\%$ water of crystallisation. If the law of constant proportions is true, then the weight of zinc required to produce $20	ext{g}$ of the zinc sulphate crystals will be:

Accepted Answer

$4.53	ext{g}$.

Answer

$45.3	ext{g}$.

Answer

$0.453	ext{g}$.

Answer

$453	ext{g}$.

Question 3

What will be the molality of the solution made by dissolving $10	ext{g of } 	ext{NaOH} 	ext{ in } 100	ext{g of water}$?

Accepted Answer

$2.5	ext{m}$.

Answer

$5	ext{m}$.

Answer

$10	ext{m}$.

Answer

$1.25	ext{m}$.

Question 4

Which of the following statements is/ are incorrect?

Accepted Answer

The weight of a substance can be determined very accurately by using an analytical balance.

Answer

Volume is denoted in $	ext{dm}$ units.

Answer

Density of a substance is its amount present per unit volume.

Answer

Candela is the luminous intensity, that emits monochromatic radiation of frequency, $540 	imes 10^{12}	ext{ Hz}$.

Question 5

One mole of oxygen gas at $	ext{STP}$ is equal to:

Accepted Answer

$6.022 	imes 10^{23}$ molecules of oxygen.

Answer

$6.022 	imes 10^{23}$ atoms of oxygen.

Answer

$16	ext{g}$ of oxygen.

Answer

$32	ext{g}$ of oxygen.

Question 6

The result reported in the following multiplication of significant figures, $2.5 	imes 1.25 = 3.125$ should be:

Accepted Answer

$3.1$

Answer

$3.125$

Answer

$3.12$

Answer

$3.10$

Question 7

How many number of aluminium ions are present in $0.051	ext{g of aluminium oxide } (	ext{Al}_2	ext{O}_3)$?

Accepted Answer

$6.023 	imes 10^{20} 	ext{ ions}$.

Answer

$6.023 	imes 10^{23} 	ext{ ions}$.

Answer

$3 	ext{ ions}$.

Answer

$9 	ext{ ions}$.

Question 8

The solution of A and B are $0.1$ and $0.2$ molar in a substance. If $100	ext{mL of ‘A’}$ are mixed with $25	ext{mL of B}$ and there is no change in volume, then the final molarity of solution is:

Accepted Answer

$0.12	ext{M}$

Answer

$0.15	ext{M}$

Answer

$0.18	ext{M}$

Answer

$0.30	ext{M}$

Question 9

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?

Accepted Answer

Law of conservation of mass.

Answer

Law of definite proportions.

Answer

Law of multiple proportions.

Answer

Avogadro law.

Question 10

The weight of iron which will be converted into its oxide $(	ext{Fe}_3	ext{O}_4)$ by the action of $18	ext{g of steam}$ on it will be (Atomic weight of $	ext{Fe} = 56$):

Accepted Answer

$42	ext{g}$.

Answer

$168	ext{g}$.

Answer

$84	ext{g}$.

Answer

$21	ext{g}$.

Question 11

How many number of molecules and atoms respectively are present in $2.8	ext{L of a diatomic gas at STP}$?

Accepted Answer

$7.5 	imes 10^{22} , 15 	imes 10^{22}$

Answer

$6.023 	imes 10^{23} , 7.5 	imes 10^{23}$

Answer

$6.023 	imes 10^{23} , 15 	imes 10^{22}$

Answer

$15 	imes 10^{22} , 7.5 	imes 10^{23}$

Question 12

A gas is found to have the formula $(	ext{CO})_x$. Its vapour density is $70$. The value of $x$ will be:

Accepted Answer

$5$

Answer

$7$

Answer

$4$

Answer

$6$

Question 13

The mass of one mole of a chloride formed by metal ‘$	ext{X}$’ is $111.0	ext{g}$. Which one could be the formula of the chloride?

Accepted Answer

$	ext{XCl}_2$

Answer

$	ext{XCl}$

Answer

$	ext{XCl}_3$

Answer

$	ext{XCl}_4$

Question 14

Which law states that if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of other element, are in the ratio of small whole numbers?

Accepted Answer

Law of multiple proportions.

Answer

Avogadro’s law.

Answer

Law of definite composition.

Answer

Gay Lussac’s law of gaseous volumes.

Question 15

Which set of figures will be obtained after rounding up to three significant figures $1.386, 4.334, 2.808$?

Accepted Answer

$1.39, 4.33, 2.81$

Answer

$1.39, 4.34, 2.809$

Answer

$1.38, 4.34, 2.800$

Answer

$1.39, 4.34, 2.80$

Question 16

Total mass of the reactant is equal to the total mass of the product. This statement is related to which law?

Accepted Answer

Law of Conservation of Mass

Answer

Law of Mass Action

Answer

Law of Multiple Proportion

Answer

Avogadro's Law

Question 17

The number $6.022 	imes 10^{23}$ entities (atoms/molecules) in one mole is known as:

Accepted Answer

Avogadro's Number

Answer

Planck's Constant

Answer

Equilibrium Constant

Answer

Exponential Constant

Question 18

Which of the following correctly represents $180	ext{ gram of water}$?

Accepted Answer

$6.023 	imes 10^{24}$ molecules of water

Answer

$5	ext{ mol of water}$

Answer

$1	ext{ mol of water}$

Answer

$6.023 	imes 10^{23}$ molecules of water

Question 19

A solution contains $6.02 	imes 10^{20}$ molecules of Urea in $100	ext{ mL of its solution}$. The concentration (Molarity) of the solution is:

Accepted Answer

$0.01	ext{ M}$

Answer

$0.02	ext{ M}$

Answer

$0.2	ext{ M}$

Answer

$0.1	ext{ M}$

Question 20

An organic compound has an empirical formula $	ext{CH}_2	ext{O}$. Its vapour density is $45$. The molecular formula is:

Accepted Answer

$	ext{C}_3	ext{H}_6	ext{O}_3$

Answer

$	ext{CH}_2	ext{O}$

Answer

$	ext{C}_2	ext{H}_5	ext{O}$

Answer

$	ext{C}_6	ext{H}_{12}	ext{O}_6$

Question 21

$2	ext{g of substance A}$ (solute) is mixed with $18	ext{g of substance B}$ (solvent). Calculate the mass percentage of the solute (A).

Accepted Answer

$10\%$

Answer

$8\%$

Answer

$9\%$

Answer

$20\%$

Question 22

What is the mole fraction of the solute in one molal aqueous solution?

Accepted Answer

$0.0177$

Answer

$0.177$

Answer

$1.77$

Answer

$0.77$

Question 23

What is the molarity of pure water? ($	ext{Density } 1	ext{ g/mL}$)

Accepted Answer

$55.6	ext{ M}$

Answer

$18	ext{ M}$

Answer

$100	ext{ M}$

Answer

$50	ext{ M}$

Question 24

$750	ext{ mL of } 0.5	ext{ M HCl}$ is mixed with $250	ext{ mL of } 2	ext{ M HCl}$. What is the final molarity of the solution?

Accepted Answer

$0.875	ext{ M}$

Answer

$1.0	ext{ M}$

Answer

$1.5	ext{ M}$

Answer

$2.5	ext{ M}$

Question 25

How much copper can be obtained from $100	ext{ gram of Copper Sulphate } (	ext{CuSO}_4)$? (Atomic weight $	ext{Cu} = 63.5$)

Accepted Answer

$39.8	ext{ g}$

Answer

$45.79	ext{ g}$

Answer

$35.8	ext{ g}$

Answer

$41.5	ext{ g}$

Question 26

What will be the mass of one $	ext{Carbon-12}$ atom in grams?

Accepted Answer

$1.9927 	imes 10^{-23}	ext{ g}$

Answer

$1.9927 	imes 10^{-24}	ext{ g}$

Answer

$12	ext{ g}$

Answer

$2.0 	imes 10^{-23}	ext{ g}$

Question 27

Which of the following reaction is NOT correct according to the Law of Conservation of Mass?

Accepted Answer

$	ext{C}_3	ext{H}_8 + 	ext{O}_2 	o 	ext{CO}_2 + 	ext{H}_2	ext{O}$

Answer

$2	ext{Mg} + 	ext{O}_2 	o 2	ext{MgO}$

Answer

$4	ext{P} + 5	ext{O}_2 	o 	ext{P}_4	ext{O}_{10}$

Answer

$	ext{H}_2 + 	ext{Cl}_2 	o 2	ext{HCl}$

Question 28

Which of the following term is unitless?

Accepted Answer

Mole fraction

Answer

Molality

Answer

Molarity

Answer

Percentage by mass

Question 29

Choose the incorrect match regarding SI units:

Accepted Answer

Unit of Time: $	ext{minute}$

Answer

Amount of substance: $	ext{mole}$

Answer

Luminous Intensity: $	ext{candela}$

Answer

Unit of Length: $	ext{meter}$

Question 30

Calculate the Molecular Weight if the Vapour Density is $22$.

Accepted Answer

$44$

Answer

$32$

Answer

$36$

Answer

$64$

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Some Basic Concepts of Chemistry Set-1

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