CBSE Class 11 Chemistry Basic Concepts Of Chemistry

Question. If a compound contains two oxygen atoms, four carbon atoms and number of hydrogen atoms is double of carbon atoms, the vapour density of it is :
(A) 88
(B) 44
(C) 132
(D) 72
Answer. B

Question. Analysis of a sample of a compound shows that it contains 24.3% carbon, 4.1% hydrogen and 71.6% chlorine. The empirical formula of the compound is -
(A) C₂H₄Cl₂
(B) C₂H₂Cl
(C) CH₂Cl₂
(D) CHCl₃
Answer. A

Question. The density of air is 0.001293 g/ml at S.T.P. Its vapour density will be :
(A) 10
(B) 15
(C) 1.44
(D) 14.4
Answer. D

Question. 14 g of element X combine with 16 g of oxygen. One the basis of this information, which of the following is a correct statement ?
(A) The element X could have an atomic weight of 7 and its oxide is XO.
(B) The element X could have an atomic weight of 14 and its oxide is X₂O.
(C) The element X could have an atomic weight of 7 and its oxide is X₂O.
(D) The element X could have an atomic weight of 14 and its oxide is XO₂ .
Answer. C

Question. On analysis a certain compound was found to contain iodine and oxygen in the ratio 254 g of iodine and 80 g of oxygen. The atomic mass of iodine is 127 and that of oxygen is 16. Which is the formula of the compound ?
(A) IO
(B) I₂O
(C) I₅O₂
(D) I₂O₅
Answer. D

Question. On standard temperature and pressure, the volume of 7.1 kg of Cl₂ will be :
(A) 2240 L
(B) 2.24 L
(C) 224 L
(D) 4.48 L
Answer. A

Question. Which of the following has the smallest number of molecules ?
(B) 22.4
(A) 2 gm H L SO₂ gas at NTP 2 gas
(C) 1 mole SO₂ gas
(D) 35.5 gm Cl₂ gas
Answer. D

Question. How many litres of O₂ gas at STP or NTP is needed to react completely with 27 gm of Al ?
(A) 5.6 lit.
(B) 11.2 lit.
(C) 22.4 lit.
(D) 16.8 lit.
Answer. D

Question. The ratio of molecules present in 4.4 g of CO₂ and 0.56 L (at STP) of SO₂ is : (At. mass : C = 12,O = 16, S = 32)
(A) 2 : 1
(B) 4 : 1
(C) 8 : 1
(D) 3 : 2
Answer. B

Question. 8g of sulphur is burnt to form SO₂, which is oxidised by Cl₂ water. The solution is treated with BaCl₂ solution. The amount of BaSO₄ precipitated is -
(A) 1.0 mole
(B) 0.5 mole
(C) 0.75 mole
(D) 0.25 mole
Answer. D

Question. The percentage of P₂O₅ in diammonium hydrogen phosphate is -
(A) 77.58
(B) 46.96
(C) 53.78
(D) 23.48
Answer. C

Question. 100 mL of 0.5 N NaOH were added to 20 ml of 1N HCl and 10 mL of 3 N H₂SO₄. The solution is -
(A) acidic
(B) basic
(C) neutral
(D) none of these
Answer. C

Question. When FeCl₃ is ignited in an atmosphere of pure oxygen, the following reaction takes place-
4FeCl₃(s) + 3O₂(g) → 2Fe₂O₃(s) + 6Cl₂(g)
If 3 moles of FeCl₃ are ignited in the presence of 2 moles of O₂ gas, how much of which reagent is present in excess and therefore, remains unreacted ?
(A) 0.33 mole FeCl₃ remains unreacted
(B) 0.67 mole FeCl₃ remains unreacted
(C) 0.25 mole O₂ remains unreacted
(D) 0.50 mole O₂ remains unreacted
Answer. A

Question. What volume of 0.8 M solution contains 0.1 mole of solute ?
(A) 100 mL
(B) 125 mL
(C) 500 mL
(D) 0.125 L
Answer. D

Question. Which of the following statements is not correct ?
(A) the number of molecules in 1 gm H₂ is greater than the number of molecules in 1 gm CO₂
(B) the number of atoms in 1 gm of an element is not equal to the number of atoms in 1 gm atom of element
(C) the modern atomic mass unit is based on the mass of 12C isotopes of carbon
(D) none of these
Answer. D

Question. The number of molecules in 16 g of methane is-
(A) 30×10²³
(B) 6.02
(C) 16/6.02×10²³
(D) 16/3.0×10²³
Answer. B

Question. Which of the following statement is correct :
(A) 1 mole of electrons has 1.6 × 10^–19 C of charge.
(B) 1 mole of electron weighs 0.54 mg
(C) 1 mole of electrons weighs 5.4 mg
(D) 1 mole of electrons weighs 0.54 kg
Answer. B

Question. The hourly energy requirement of an astronaut can be satisfied by the energy released when 34 g of sucrose (C₁₂H₂₂O₁₁) are burnt in his body. How many g of oxygen would be needed to be carried in space capsule to meet his requirement for one day -
(A) 916.2 gm
(B) 91.62 gm
(C) 8.162 gm
(D) 9.162 gm.
Answer. A

Question. Minimum amount of Ag₂CO₃ (s) required to produce sufficient oxygen for the complete combustion of C₂H₂ which produces 11.2 ltr of CO₂ at S.T.P after combustion is: [Ag = 108]
Ag₂CO₃ (s) → 2Ag (s) + CO₂ (g) + 1 2O₂ (g)
C₂H₂ + 5/2O₂ → 2CO₂ + H₂O
(A) 276 g
(B) 345 g
(C) 690 g
(D) 1380 g
Answer. B

Question. Consider the following statements
1.If all the reactants are not taken in their stoichiometric ratio, then at least one reactant will be left behind.
2.2 moles of H₂(g) and 3 moles of O₂(g) produce 2 moles of water.
3.equal wt. of carbon and oxygen are taken to produce CO₂ then O₂ is limiting reagent.
The above statements 1, 2, 3 respectively are
(T = True, F = False)
(A) T T T
(B) F T F
(C) F F F
(D) T F T
Answer. A

Question. The density of 3M sodium thiosulphate is 1.25 g/ml. Identify the correct statements among the following :
(A) % by weight of sodium thisoulphate is 37.92
(B) The mole fraction of sodium thisoulphate is 0.065
(C) The molarity of Na⁺ is 2.53 and S₂O₃^2– is 1.25
(D) (A) & (B) both
Answer. D

Question. Silver metal in ore is dissolved by potassium cyanide solution in the presence of air by the reaction
4 Ag + 8 KCN + O₂ + 2H₂O → 4 K[Ag (CN)₂] + 4 KOH
(A) The amount of KCN required to dissolve 100 g of pure Ag is 120 g.
(B) The amount of oxygen used in this process is 7.40 g (for 100 gm pure Ag)
(C) The volume of oxygen used at STP is 5.19 litres for the same process.
(D) all of these are correct
Answer. D

Question. For the reaction 2P + Q → R, 12 mol of P and 8 mol of Q are taken then
(A) 3 mol of R is produced
(B) 6 mol of R is produced
(C) 25% of Q is left behind
(D) Both (B) and (C) are correct
Answer. D

Question. A solution containing 0.1 mol of a metal chloride MClx requires 500 ml of 0.8 M AgNO₃ solution for
complete reaction MClx + xAgNO₃ → xAgCl + M(NO₃)x. Then the value of x is -
(A) 1
(B) 2
(C) 4
(D) 3
Answer. C

Question. When burnt in air, a 12.0 g mixture of carbon and sulphur yields a mixture of CO₂ and SO₂, in which the number of moles of SO₂ is half that of CO₂. The mass of the carbon the mixture contains is (At. wt. S = 32)
(A) 4.08 g
(B) 5.14 g
(C) 8.74 g
(D) 1.54 g
Answer. B

Question. The haemoglobin from the red blood corpuscles of most mammals contains approximately 0.33% of iron by weight. The molecular weight of haemoglobin as 67,200. The number of iron atoms in each molecule of haemoglobin is (atomic weight of iron = 56) :
(A) 2
(B) 3
(C) 4
(D) 5
Answer. C

Question. On adding 20 mL of 0.1 N NaOH solution to 10 mL of 0.1 N HCl, the resulting solution will :
(A) Turn blue litmus red
(B) Turn phenolphthalein solution pink
(C) Turn methyl orange red
(D) Will have no effect on red or blue litmus paper.
Answer. B

Question. The isotopic abundance of C–12 and C–14 is 98% and 2% respectively. What would be the number of C–14 isotope in 12 g carbon sample ?
(A) 1.032×10²²
(B) 3.01×10²³
(C) 5.88×10²³
(D) 6.02×10²³
Answer. A

Question. Amount of oxygen required for combustion of 1 kg of a mixture of butane and isobutane is :
(A) 1.8 kg
(B) 2.7 kg
(C) 4.5 kg
(D) 3.58 kg
Answer. D

Question. The dehydration yield of cyclohexanol to cyclohexene is 75%. What would be the yield if 100 g of cyclohexanol is dehydrated ?
(A) 61.7 g
(B) 16.5 g
(C) 6.15 g
(D) 615 g
Answer. A 

Question. In a chemical reaction one molecule of hydrogen sulphide gas reacts with two molecules of nitric acid.
The molecules of nitrogen dioxide and water and atoms of sulphur formed has a ratio of -
(A) 1 : 2 : 2
(B) 2 : 1 : 2
(C) 2 : 2 : 1
(D) 1 : 1 : 1
Answer. C

Question. Molecular formula of a compound of metal M (equivalent weight 8) is M₂CO₃ . Atomic weight of the metal will be - 
(A) 24
(B) 16
(C) 8
(D) 4
Answer. C

Question. The quantity of potassium chlorate (molecular weight 122.5) required in grams to produce 33.6 litre of oxygen at normal temperature and pressure will be -
(A) 122.5
(B) 132.6
(C) 245.0
(D) 254.0
Answer. A

Question. The group of symbols of elements based on Latin names out of the following is -
(A) Ca, Ag, Cu
(B) Ag, Au, K
(C) Pb, Cl, Cd
(D) Cs, Fe, Na
Answer. B

 

1 Mark question

1. What is the number of significant figures in 0.001620?
2. Calculate the percentage of nitrogen in NH₃.
3. Calculate molecular mass of C₆H₁₂O₆ molecule.
4. State the law of multiple proportion.
5. How many atoms of Calcium are there in 2g of Ca?

2 marks Question:

6. Define element, compound and mixture.
7. Define Gay Lussac’s law of gaseous volumes. Explain with one suitable example.
8. An organo metallic compound on analysis was found to contain C=64.4% , H=5.5 % and Fe= 29.9 %. Determine its empirical formula. ( At mass of Fe= 564)
9. What volume of 6M Hcl and 2MHcl should be mixed to get two litres of 3M Hcl?
 

Unit 1 SOME BASIC CONCEPTS OF CHEMISTRY

1 mark question

1. What is the number of significant figures in 0.001620?

2. Calculate the percentage of nitrogen in NH_3.

3. Calculate molecular mass of C₆H₁₂O₆ molecule.

4. State the law of multiple proportion.

5. How many atoms of Calcium are there in 2g of Ca?

2 marks Question:

6. Define element, compound and mixture.

7. Define Gay Lussac’s law of gaseous volumes. Explain with one suitable example.

8. An organo metallic compound on analysis was found to contain C = 64.4% , H = 5.5 % and
Fe = 29.9 %. Determine its empirical formula. ( At mass of Fe = 564)

9. What volume of 6M Hcl and 2MHcl should be mixed to get two litres of 3M Hcl?

3 or more marks

10. If 20.0 g of CaCO₃ is treated with 20.0 g of HCl , how many grams of CO₂ can be
generated according to the following equation:
CaCO_3(g) + 2 HCl _(aq) CaCL_2(aq) + H₂O_(l) + CO_2(g)

11. Concentrated H2SO4 is 98% weight and has density 1.84 g cm-3. What volume of
concentrated acid is required to make 5.0 L of 0.50 M H2SO4 solution?

Unit 2 Structure of Atom

1 mark question.

1. What is the physical significance of si and si₂.

2. Write electronic configuration of Cu²⁺ and Cr^3+.

3. What is the shape of s-orbital and p-orbital

4. An atomic orbital has n=3 , what are the possible values of l?

5. State Hund,s rule of maximum multiplicity. Illustrate with an example.

6. State Pauli Exclusion Principle.

7. How many unpaired electrons are present in N? Name the principle which explains the
presence of these unpaired electrons.

2 or more marks Question:

8. Write a short note on Plank’s Quantum theory.

9. Calculate the wavelength of an electron that has been accelerated in a particle accelerator
through a potential difference of 100 million volts.

10. How does Heisenburg’s uncertainty principle support concept of orbital?

11. Calculate the uncertainty in position of dust particle with mass equal to 1 mg if the
uncertainty in velocity is 5.5 x 10^-20 ms-1 (h= 6.626 ^x 10 ^-34 JS )

12. Establish a relation between wavelength of a moving particle and its kinetic energy. The
wave length of a moving particle of mass 1.0 x 10^-6 Kg is 3.312 x 10 ^-29 m. calculate its
kinetic energy.( h= 6.625 ^x 10 ^-34 JS )

13. Define quantum numbers. Explain in brief how are different quantum numbers related to
each other?

Unit 3 Classification of elements and periodicity in properties.

1 mark question

1. State the modern periodic law.

2. What is the IUPAC name and symbol of the element with atomic n8umber 110?

3. Name the groups of elements classified as s- , p- and d - blocks.

4. Which is smallest among Na⁺, Mg²⁺, Al³⁺ and why?

5. How does electro negativity vary (i) down the group (ii) across the period from left to right?

2 or more marks Question:

6. Elements A and B have atomic number 11 and 24 respectively. Write their electronic
configuration and predict group, period and block to which they belong. Which of them is
representative element?

7. a) Write general configuration of transition and inner transition elements.
b) Explain the following
i. Electron affinity of chlorine is more than of fluorine.
ii. I.E of nitrogen is greater than that of oxygen.

8. a) Why is ionization enthalpy of Be higher than Boron?
b) Why is second ionization energy of group -1 elements very high?

9. State the group to which elements having following electronic configuration belong:
i. [Ar]⁴s²³d¹
ii. [Kr]⁵s¹
iii. [Ar]⁴s²³d¹⁰4p⁵
iv. [Ar]⁴s¹³d¹⁰

Unit 4 Chemical bonding and molecular structure.

1 mark question

1. What is meant by electrovalent or ionic bond?

2. Write Lewis dot structure of Br, N^3- , Ca ²⁺ , Mg , O.

3. Why is water liquid whereas H₂S gas at room temperature?

4. Draw Lewis structure for the following molecules. CCl₄, Co₃^2- , PCl₅, H₂O, N₂

5. What are two types of H- bonding? Which of them is stronger?

6. What is the state of hybridization of O in H₂O?

2 or more marks Question:

7. Write the molecular orbital configuration of the species O₂- and C₂

8. What is meant by VSEPR theory? Explain the shape of PCL₅ using VSEPR theory.

9. a) What is sigma bond stronger than π bond?
b) Why does Be₂ not exist?

10. Discuss the shape of following molecule on the basis of hybridization.
i) CH₄ ii) CH₂= CH₂ iii) HC= CH

11. Explain the term hybridization taking CH≡ CH as an example.

12. What are the main points of similarity and difference between valence bond theory and molecular orbital theory?

 

ONE MARK QUESTIONS

1. State the law of multiple proportions.

2. 100ml of 10M HCl is diluted with water to 2 L. Find the molarity of the solution.

3. What is the effect of temperature on molarity and molality?

4. Define the terms empirical formula and molecular formula.

5. Why do atomic masses of most of the elements in atomic mass unit involve fraction?

6. What do you understand by the term limiting reagent?

7. How many atoms are there in a) 72 u of Carbon b) 72 g of carbon.

8. 400 mL each of H₂ and O₂ are mixed and ignited, find volume of water vapour formed?
 

TWO MARKS QUESTIONS

1 Calculate the mass of the following in Kg

(i) one calcium atom

(ii) one molecule of water

2 Sulphur forms two gaseous oxides. One of these oxides contains 50 % sulphur while the other contains 40 % of sulphur. Show that these data illustrate the law of multiple proportions

3 6.5g of Zn was reacted with excess of dil. HCl. Calculate the amount and volume of hydrogen produced at STP.

4 4.8g of O₂ was used to burn 0.15moles of Fe to Fe₂O₃. What mass of Fe₂O₃ was formed?

5 A compound contains 2.68% Mg. How many atoms of magnesium are present in 15g of the compound

6 Calculate the percentage of (i) copper (ii) sulphur (iii) oxygen and (iv) water of hydration in crystalline copper sulphate, CuSO₄.5H₂O.

7 A higher oxide contains 80% metal. 0.72g of lower oxide gave 0.8g of higher oxide when oxidized. Show that this is in agreement with the law of multiple proportions.

8 1.8g of an organic compound on combustion gave 2.64g of CO₂ and 1.08g of water. Find the empirical formula of the compound.

9 Calculate the number of atoms and molecules in 224ml of Nitrogen gas at STP.

10 Find the number of atoms of each type in 3.42g of sucrose (C₁₂H₂₂O₁₁).

11 What mass C¹² will contain the same number of atoms as in 3.6g of O¹⁶?

12 Calculate mass of CO₂ containing same number of oxygen atoms as in 3g of NO.

13 From 0.2g of CO₂, 10²¹ molecules are removed. How many of moles of CO₂ remain?

14 Calculate the mole fraction of ethanol in 0.5 m aqueous solution of ethanol.

15 The mole fraction of glucose in water is 0.35. What is the molality of the solution?
 

THREE MARKS QUESTIONS

1 Commercially available H₂SO₄ contains 98% acid by mass. Find the molarity if density of the
sample is 1.84g/cc. What volume of this acid is required to make 2 L of 0.1 M solution?

2 200ml of 0.05M magnesium chloride is mixed with 75ml of 0.1M silver nitrate solution. Find the number of moles and mass in grams of AgCl formed. What is the limiting reagent?

3 (i) 24g of NaOH is dissolved in 300ml water. Calculate the molarity of the solution.
(ii) The density of a 3M solution of NaCl is 1.25g/mL. Calculate the molality of the solution.

4 Aqueous magnesium chloride solution is marketed as 20% by mass. Its density is 1.18 g/ml. 
Calculate
(i) The mole fraction of each component
(ii) Molarity.
(iii) Molality

5 Define
(i) molarity, (ii) molality , (iii) mole fraction.

6 A hydrocarbon on burning gave 3.38g of CO₂ and 0.69g of H₂O. 10 L of the gas at STP weighs 11.6g. Find empirical and molecular formula.