Chemistry

Some Basic Concepts of Chemistry

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Some Basic Concepts of Chemistry

Q 1.

Match the following prefixes with their multiples:
ncert-solutions-for-class-11-chemistry-chapter-1-some-basic-concepts-of-chemistry-15

Q 2.

How many oxygen atoms are there in 18 g of water?

Q 4.

Name two factors that introduce uncertainty into measured figures.

Q 5.

What is one a.m.u. or one ‘u’?

Q 6.

What do you understand by stoichiometric coefficients in a chemical equation?

Q 7.

Calculate the amount of carbon dioxide that could be produced when
(i) 1 mole of carbon is burnt in air.
(ii) 1 mole of carbon is burnt in 16 g of dioxygen.
(iii) 2 moles of carbon are burnt in 16 g of dioxygen.

Q 8.

How much copper can be obtained from 100 g of copper sulphate (CuSO4  )? (Atomic mass of Cu= 63.5 amu)

Q 9.

What do you mean by significant figures?

Q 10.

Round up the following upto three significant figures:
(i) 34.216 (ii) 10.4107 (iii) 0.04597 (iv) 2808

Q 11.

Calculate the atomic mass (average) of chlorine using the following data:
ncert-solutions-for-class-11-chemistry-chapter-1-some-basic-concepts-of-chemistry-9

Q 12.

State Avogadro’s law.

Q 13.

Pressure is determined as force per unit area of the surface. The S.I. unit of pressure, pascal, is as shown below:1 Pa = 1  Nm-2.If mass of air at sea level is 1034 g  cm-2,calculate the pressure in pascal.

Q 14.

Define molality. How does molality depend on temperature?

Q 15.

Define the term ‘unit’ of measurement.

Q 16.

The density of water at room temperature is 1.0 g/mL. How many molecules are there in a drop of water if its volume is 0.05 mL?

Q 17.

In the reaction, A + B2——> AB2, identify the limiting reagent, if any, in the following  mixtures
(i) 300 atoms of A + 200 molecules ofB
(ii) 2 mol A + 3 mol B
(iii) 100 atoms of A + 100 molecules ofB
(iv) 5 mol A + 2.5 mol B
(v) 2.5 mol A + 5 mol B

Q 18.

How are 0.50 mol  Na2C03  and 0.50 M  Na2C03  different?

Q 19.

Calculate the mass of sodium acetate (CH3COONa) required to make 500 mL of 0.375 molar aqueous solution. Molar mass of sodium acetate is 82.0245 g  mol-1

Q 20.

Give an example of a molecule in which the ratio of the molecular formula is six times the empirical formula.

Q 21.

What is the molecular mass of a substance each molecule of which contains 9 atoms of carbon, 13 atoms of hydrogen and 2.33 x  10-23  g other component?

Q 22.

Express the following up to four significant figures.
ncert-solutions-for-class-11-chemistry-chapter-1-some-basic-concepts-of-chemistry-38

Q 23.

Q 24.

Calculate the molecular mass of the following:
(i)  H20(ii)  C02(iii)  CH4

Q 25.

Chlorine is prepared in the laboratory by treating manganese dioxide (Mn02) with aqueous hydrochloric acid according to the reaction.
4 HCl (aq) + Mn02 (s) ———–> 2 H2O (l) + MnCl2(aq) +Cl2(g)

How many grams of HCl react with 5.0 g of manganese dioxide? (Atomic mass of Mn = 55 u)

Q 26.

What is the SI unit of molarity?

Q 27.

Use the data given in the following table to calculate the molar mass of naturally occurring argon.
ncert-solutions-for-class-11-chemistry-chapter-1-some-basic-concepts-of-chemistry-30

Q 28.

What is the S.I. unit of mass?

Q 29.

The cost of table salt (NaCl) and table sugar (C12H22O11) are Rs 1 per kg and Rs 6 per kg respectively.Calculate their cost per mole.

Q 30.

Determine the empirical formula of an oxide of Iron which has 69.9 % iron and 30.1 % dioxygen by mass.

Q 31.

The following data were obtained when dinitrogen and dioxygen react together to form compounds:
ncert-solutions-for-class-11-chemistry-chapter-1-some-basic-concepts-of-chemistry-19

Q 32.

Why air is not always regarded as homogeneous mixture?

Q 33.

What is the number of significant figures in 1.050 x 104?

Q 34.

Calculate the concentration of nitric acid in moles per litre in a sample which has a density 1.41 g  mL-1  and the mass percent of nitric acid in it is being 69%.

Q 35.

Calculate the mass percent of different elements present in sodium sulphate (Na2 SO4).

Q 36.

Dinitrogen and dihydrogen react with each other to produce ammonia according to the following chemical equation:(i)  N2 (g) + 3H2(g) —–> 2NH3 (g)
(ii) Will any of the two reactants remain unreacted?
(iii) If yes, which one and what would be its mass?

Q 37.

Calculate the number of atoms in each of the following:
(i) 52 moles of He (ii) 52 u of He (iii) 52 g of He

Q 38.

If the density of methanol is 0.793 kg  L -1, what is its volume needed for making 2.5 L of its 0.25 M solution?

Q 39.

How many significant figures should be present in the answer of the following?
ncert-solutions-for-class-11-chemistry-chapter-1-some-basic-concepts-of-chemistry-29

Q 40.

How is empirical formula of a compound related to its molecular formula?

Q 41.

Calculate the number of moles in each of the following.

Q 42.

Calcium carbonate reacts with aqueous HCl according to the reaction

CaC03 (s) + 2HCl (aq) ———->CaCl2  (aq) +C02(g) +H2O(l).

What mass of CaC03 is required to react completely with 25 mL of 0.75 M HCl?

Q 43.

KCl03  on heating decomposes to give KCl and 02. What is the volume of  02 at N.T.P liberated by 0.1 mole of  KCl03?

Q 44.

Determine the molecular formula of an oxide of iron in which the mass percent of iron and oxygen are 69.9 and 30.1 respectively. Given that the molar mass of the oxide is 159.8 g  mol-1(Atomic mass: Fe = 55.85, O = 16.00 amu)Calculation of Empirical Formula.

Q 45.

In three moles of ethane (C2H6), calculate the following:
(i) Number of moles of carbon atoms (ii) Number of moles of hydrogen atoms
(iii) Number of molecules of ethane

Q 46.

Which one of the following will have largest number of atoms?
(i) 1 g Au (s) (ii) 1 g Na (s) (iii) 1 g Li (s) (iv) 1 g of  Cl2(g)  (Atomic masses: Au = 197, Na = 23, Li = 7, Cl = 35.5 amu)

Q 47.

Calculate no. of carbon and oxygen atoms present in 11.2 litres of  C02  at N.T.P.

Q 48.

Express the following in scientific notation:
(i) 0.0048 (v) 6.0012 (ii) 234,000 (iii) 8008 (iv) 500.0

Q 49.

How many significant figures are present in the following?
(i) 0.0025 (ii) 208 (iii) 5005 (iv) 126,000
(v) 500.0 (vi) 2.0034

Q 50.

Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is 0.040.