[PDF] CBSE NCERT Solutions for Class 11 Chemistry Chapter 1 - Back

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Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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CBSE NCERT Solutions for Class 11 Chemistry Chapter 1

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1. Calculate the molar mass of the following:

(iii) ସs

Solution:

oxygen) ൌ(ͳൈ Atomic mass of carbon)൅(ʹൈ Atomic mass of oxygen) (iii) The molecular mass of methane ( ସ) Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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dioxygen by mass.

Solution:

Relative moles of oxygen in iron oxide:

Simplest molar ratio of iron to oxygen:

4. Calculate the amount of carbon dioxide that could be produced when

(i) ͳ mole of carbon is burnt in air. (ii) ͳ mole of carbon is burnt in ͳ͸ of dioxygen. (iii) ʹ moles of carbon is burnt in ͳ͸ of dioxygen. Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

The balanced reaction of combustion of carbon can be written as: Initial mole 1 1 െ Left mole ͳെͳൌͲ ͳെͳൌͲ 1 As per stoichiometry of the balanced equation, ͳ mole of carbon burns in ͳ mole of dioxygen (air) to Produced ͳ mole of carbon dioxide. (ii) ͳ mole of carbon is burnt in ͳ͸ of dioxygen. Given in question : dioxygen= ͳ͸ ; mole of carbon = 1

We know : ൌ୫୭୪ୣୱ

According to the stoichiometry of the balanced equation (ʹʹ). Hence, dioxygen is a limiting reactant. Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

Volume of solution = 500 ml

solution (litre)

6. Calculate the concentration of nitric acid in moles per liter in a sample which has a

Solution:

Mass percent of nitric acid in the sample ൌ͸ͻΨ Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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We know, the mass percent of nitric acid in it being ͸ͻΨൌ ͳͲͲ of nitric acid contains

͸ͻ of nitric acid by mass.

Concentration of nitric acidൌ୫୭୪ୣ

Solution:

Given : mass of ସൌ 100 g

Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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8. Determine the molecular formula of an oxide of iron, in which the mass percent of iron

Solution:

We know : The atomic mass of iron = 55.85

The atomic mass of oxygen = 16

The ratio of iron to oxygen in the oxide,

ൌͳ(approx) Molecular formula of a compound = (empirical formula of a compound) . Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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9. Calculate the atomic mass (average) of chlorine using the following data:

Ψ Natural

Abundance

Molar Mass

Solution:

given in question :

The average atomic mass of chlorine.

(i) Number of moles of carbon atoms. (ii) Number of moles of hydrogen atoms. (iii) Number of molecules of ethane.

Solution:

Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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ൌʹൈ͵ൌ͸ moles of carbon ൌ͵ൈ͸ൌͳͺ moles of hydrogen atoms ethane. enough water to make a final volume up to ʹ?

Solution:

Given mass of glucose = 20 g

By putting the values in formula we get

Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

Given:

13. Pressure is determined as force per unit area of the surface. The unit of pressure, pascal

is as shown below:

Solution:

The pressure is defined as force acting per unit area of the surface. Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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We know,

Then,

14. What is the unit of mass? How is it defined?

Solution:

ͳ kilogram is defined as the mass equal to the mass of the international prototype(Platinum-Iridium cylinder in Paris) of the kilogram.

15. Match the following prefixes with their multiples:

Prefixes Multiples

(i) Micro ͳͲ଺ (ii) Deca ͳͲଽ (iii) Mega ͳͲି଺ (iv) Giga ͳͲିଵହ (v) Femto ͳͲ

Solution:

Prefixes Multiples

(i) Micro ͳͲି଺ (ii) Deca ͳͲ (iii) Mega ͳͲ଺ (iv) Giga ͳͲଽ (v) Femto ͳͲିଵହ Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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16. What do you mean by significant figures?

Solution:

Significant figures are those meaningful digits that are known with certainty. They result of an experiment, then ʹͷ is certain, while ͺ is uncertain, and the total number of significant figures are ͵. Hence, significant figures are defined as the total number of digits in a number including the last digit that represents the uncertainty of the result.

17. A sample of drinking water was found to be severely contaminated with chloroform

ଷ supposed to be carcinogenic in nature. The level of contamination was ͳͷ ppm (by mass). (i) Express this in percent by mass. (ii) Determine the molality of chloroform in the water sample.

Solution:

Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Formula : Molaity =

Put all the above values in formula we get

Molality of chloroform in water.

18. Express the following in the scientific notation:

(iii) ͺͲͲͺ

Solution:

19. How many significant figures are present in the following?

(ii) ʹͲͺ (iii) ͷͲͲͷ Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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(iv) ͳʹ͸ǡͲͲͲ

Solution:

(i) There are ʹ significant figures. (ii) There are ͵ significant figures. (vi) There are ͵ significant figures. (vi) There are ͷ significant figures.

20. Round up the following upto three significant figures:

(iv) ʹͺͲͺ

Solution:

(iv) ʹͺͳͲ

21. The following data are obtained when dinitrogen and dioxygen react together to form

different compounds:

Mass of dinitrogen Mass of dioxygen

(iii) ʹͺ ͵ʹ (iv) ʹͺ ͺͲ Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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(a) Which law of chemical combination is obeyed by the above experimental data? Give its statement. (b) Fill in the blanks in the following conversions: (i) ͳൌ ____________ ൌ ____________ (ii) ͳൌ ____________ ൌ ____________ (iii) ͳൌ ____________ ൌ ____________ ଷ

Solution:

(a) ʹͺ Mass of dinitrogen Mass of dioxygen Ration of oxygen (iii) ʹͺ ͵ʹ 32 (iv) ʹͺ 80 (b) (i) ͳൌͳൈଵ଴଴଴୫ Hence, ͳൌͳͲ଺ൌͳͲଵହ (ii) ͳൌͳൈଵ୥ Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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(iii) ͳൌͳൈଵ୐

Solution:

distance covered by light =?

Formula : Distance traveled by light ൌൈ

Identify the limiting reagent, if any, in the following reaction mixtures. (i) ͵ͲͲ atoms of ൅ʹͲͲ molecules of (ii) ʹ൅͵ (iii) ͳͲͲ atoms of ൅ͳͲͲ molecules of Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

A reagent determines the extent of a reaction. It is the reactant which is the first to get consumed during a reaction, thereby causing the reaction to stop and limiting the amount of products formed. (i) ͵ͲͲ atoms of ൅ʹͲͲ molecules of According to the stoichiometry of reaction, ͳ atom of reacts with ͳ molecule of . Initial moles ͵ͲͲൌ͵ͲͲ୅ 200 molecule =ʹͲͲ୅ Left mole (300-200) ୅=100୅ 0 ʹͲͲ୅ (ii) ʹ൅͵ According to the reaction, ͳ of reacts with ͳ of ͵. Initial moles 2 3 െ ଵ=2 ଷ

Left mole 2-2=0 3-2=1 2

Thus, ʹ of will react with only ʹ of . As a result, ͳ of will not be consumed. Hence, is the limiting reagent. (iii) ͳͲͲ atoms of ൅ͳͲͲ molecules of According to the given reaction, ͳ atom of combines with ͳ molecule of . Initial moles ͳͲͲൌͳͲͲ୅ 100 molecule =ͳͲͲ୅ ଵ=100୅ ଵ଴଴୒ఽ Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Left mole 0 0 ͳͲͲ୅

Thus, all 100୅ moles of will combine with all 100୅ moles of . Hence, the mixture is stoichiometric where no limiting reagent is present. limiting reagent. According to the reaction, ͳ of atom combines with ͳ of molecule . Thus, left as such. Hence, is the limiting reagent.

24. Dinitrogen and dihydrogen react with each other to produce ammonia according to the

following chemical reaction: (ii) Will any of the two reactants remain unreacted? (iii) If yes, which one and what would be its mass? Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

we should know : ݉݋݈݁ܿݑ݈ܽ

Balancing the given chemical equation,

From the equation, ͳ mol of nitrogen reacts with ͵ mol of dihydrogen to give ʹ moles of ammonia. unreacted. Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

26. If ͳͲ volumes of dihydrogen gas reacts with five volumes of dioxygen gas, how many

volumes of water vapour would be produced?

Solution:

Reaction of dihydrogen with dioxygen can be written as:

Mole ratio 2 1 2 ׵ moles ן

According to stiochimerty of reaction two volumes of dihydrogen react with one volume of dioxygen to produce two volumes of water vapour. Hence, ten volumes of dihydrogen will react with five volumes of dioxygen to produce ten volumes of water vapour.

27. Convert the following into basic units:

(iii) ʹͷ͵͸ͷ Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

(iii) ʹͷ͵͸ͷ:

Since,

28. Which one of the following will have the largest number of atoms?

Solution:

Atomic mass of Au = 107

Atomic mass of Na = 23

Atomic mass of Li = 7

Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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29. Calculate the molarity of a solution of ethanol in water, in which the mole fraction of

Solution:

We know : density of water = 1 gm/ml

Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

ൌͳʹ of carbon Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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31. How many significant figures should be present in the answer of the following

calculations?

Solution:

ൌ Number of significant figures in the least precise number. Since the least number of decimal places in each term is four, the number of significant figures in the answer is also 4.

32. Use the data given in the following table to calculate the molar mass of naturally

occuring argon isotopes:

Isotope Isotopic molar mass Abundance

Class-XI-CBSE-Chemistry Some Basic Concepts Of Chemistry

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Solution:

Given :

for Isotope ଷ଺ ׷ for Isotope ଷ଼׷ for Isotope

Average molar mass

Average molar mass of argon

33. Calculate the number of atoms in each of the following

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