Chemistry

Some Basic Concepts of Chemistry

Question:

What is the concentration of sugar (C12H22O11) in mol  L -1  if its 20 g are dissolved in enough water to make a final volume up to 2 L?

Answer:

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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.

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

Q 8.

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 9.

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

Q 10.

What do you mean by significant figures?

Q 11.

State Avogadro’s law.

Q 12.

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 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.

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 27.

What is the S.I. unit of mass?

Q 28.

What is the SI unit of molarity?

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.

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 31.

Why air is not always regarded as homogeneous mixture?

Q 32.

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

Q 33.

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 34.

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

Q 35.

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

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.

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 39.

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 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.

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 43.

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

Q 44.

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 45.

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

Q 46.

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 47.

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 48.

How are 0.5 ml of NaOH differents from 0.5 M of NaOH?

Q 49.

What is the concentration of sugar (C12H22O11) in mol  L -1  if its 20 g are dissolved in enough water to make a final volume up to 2 L?

Q 50.

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