100 QUESTIONS OF SOME BASIC CONCEPTS OF CHEMISTRY CLASS XI CHAPTER NO. 01

CLASS XI

NCERT

SOME BASIC CONCEPTS OF CHEMISTRY

CHAPTER NO. 01

Q. No. 1 In the final answer of the expression

the number of significant figures is :

(a) 1 (b) 2 (c) 3 (d) 4

Q. 2 In which of the following number all zeros are significant?

(a) 0.0005 (b) 0.0500

( c) 50.000 (d) 0.0050

Q 3. The correctly reported answer of addition of 29.4406, 3.2 and 2.25 will have significant figures

(a) 3 (b) 4

( c) 2 (d) 5

Q. 4 20 g of CaCO₃ on heating gave 8.8 g of CO₂ and 11.2 g of CaO. This is in accordance with

1. The law of conservation of mass.
2. The law of constant composition.
3. The law of reciprocal proportion.
4. None of these

Q. 5 Irrespective of the source, pure sample, of water always yields 88.89% mass of oxygen and

11.11% mass of hydrogen. This is explained by the law of

(a) conservation of mass (b) multiple proportions

( c) constant composition (d) constant volume

Q. 6 Which one of the following pairs of compounds illustrate the law of multiple proportions ?

(a) H₂O and Na₂O (b) MgO and Na₂O

( c) Na₂O and BaO (d) SnCl₂ and SnCl₄

Q. 7 Two students performed the same experiment separately and each one of them recorded two readings of mass which are given below. Correct reading of mass is 3.0 g. On the basis of given data, mark the correct option out of the following statements.

Students Readings

(i) (ii)

1. 3.01 2.99
2. 3.05 2.95
3. Results of both the students are neither accurate nor precise.
4. Results of student A are both precise and accurate.
5. Results of student B are neither precise nor accurate.
6. Results of student B are both precise and accurate.

Q. 8 The molecular weight of O₂ and SO₂ are 32 and 64 respectively. At 15°C and 150 mm Hg pressure, one litre of O₂ contains ‘N’ molecules. The number of molecules in two litres of SO₂ under the same conditions of temperature and pressure will be :

(a) N/2 (b) 1N ( c) 2N (d) 4N

Q. 9 10 dm³ of N₂ gas and 10 dm³ of gas X at the same temperature contain the same number of molecules, the gas X is

(a) CO₂ (b) CO

( c) H₂ (d) NO

Q. 10 The percentage weight of Zn in white vitriol [ZnSO₄.7H₂O] is approximately equal to

(Zn = 65,S =32, O = 16 and H = 1)

(a) 33.65 % (b) 32.56 % ( c) 23.65 % (d) 22.65 %

Q. 11 What is the average atomic mass of bromine from the following data :

(abundance is in %)

Isotope	Mass	Abundance
79Br	78.9183361	50.69
81Br	80.916289	49.31

(a) 79.9 (b) 76.6

( c) 75.9 (d) 69.9

Q. 12 Calculate the volume at STP occupied by 240 gm of SO₂.

(a) 64 (b) 84 (c) 59 (d) 73

Q. 13 If the mass of the one atom is found to be 2.324784×10^–23g, then this atom can be ?

(a) Oxygen (b) Carbon

( c) Fluorine (d) Nitrogen

Q. 14 At S.T.P. the density of CCl₄ vapours in g/L will be nearest to:

(a) 6.87 (b) 3.42 ( c) 10.26 (d) 4.57

Q. 15 The number of O-atoms in 4.4 grams of CO₂ are

(a) 1.2 × 10²³ (b) 6 × 10²² ( c) 6 × 10²³ (d) 12 × 10²³

Q. 16 How many atoms are contained in one mole of sucrose (C₁₂ H₂₂O₁₁)?

(a) 20 × 6.02 × 10²³ atoms/mol (b) 45 × 6.02 × 10²³ toms/mol

(c) 5 × 6.02 × 10²³ atoms/mol (d) None of these

Q. 17 Number of moles of NaOH present in 2 litre of 0.5 M NaOH is:

(a) 1.5 (b) 2.0 ( c) 1.0 (d) 2.5

Q. 18 10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. Amount of water produced in this reaction will be:

(a) 3 mol (b) 4 mol ( c) 1 mol (d) 2 mol

Q. 19 The simplest formula of a compound containing 50% of element X (atomic mass 10) and 50% of element Y (atomic mass 20) is

(a) XY (b) XY₃ (c) X₂Y (d) X₂Y₃

Q. 20 12 gm of Mg (atomic mass 24) will react completely with hydrochloric acid to give

1. One mol of H₂
2. 1/2 mol of H₂
3. 2/3 mol of O₂
4. both 1/2 mol of H2 and 1/2 mol of O2

Q. 21 Which of the following statements about a compound is incorrect?

1. A molecule of a compound has atoms of different elements.
2. A compound cannot be separated into its constituent elements by physical methods of separation.
3. A compound retains the physical properties of its constituent elements.
4. The ratio of atoms of different elements in a compound is fixed.

Q. 22 Which of the following statements are correct ?

1. Both solids and liquids have definite volume.
2. Both liquids and gases do not have definite shape.
3. Both solids and gases take the shape of the container.

(a) (i) and (iii) (b) (ii) and (iii)

( c) (i) and (ii) (d) (i), (ii) and (iii)

Q. 23 Read the following and choose the incorrect statements.

1. Both weight and mass are same quantities used for measurement of amount of matter present in a substance
2. Mass and weight of a substance vary from one place to another due to change in gravity.
3. SI unit of mass is kilogram and while SI unit of weight is gram.

(a) (i) and (iii) (b) (ii) and (iii)

( c) (i) and (ii) (d) All of these

Q. 24 Consider the following statements.

1. Atoms of H, O, N and C have identical properties but different mass.
2. Matter is divisible into atoms which are further indivisible.
3. The ratio of N: H in NH₃ is 1 : 3 and N : O in nitric oxide is 2 : 1.
4. Dalton’s atomic theory support law of conservation of mass.

Which of the following pairs of statements is true according to Dalton’s atomic theory ?

(a) (i) and (ii) (b) (ii) and (iii)

( c) (ii) and (iv) (d) (i) and (iv)

Q. 25 Give the correct order of initials T or F for following statements. Use T if statement is true and F if it is false.

1. Gay-Lussac’s law of gaseous volumes is actually the law of definite proportion by volume.
2. Law of conservation of mass is true for physical change, but not for chemical change.
3. The percentage of oxygen in H₂O₂ is different from that in H₂O. Hence, it violates law of definite proportions.
4. Fixed mass of A reacts with two different masses of B (say x and y), then the ratio of x/y can be any positive integer.
5. At STP, 5 mL of N₂ and H₂ have different no. of molecules.

(a) TTFTF (b) FTTFT

( c) TFFTF (d) TFTTF

Q. 26 Match the columns

	Column-I	Column-II
	(Laws of chemical combinations)	(Scientist)
(A)	Law of definite proportions	(p) Antoine Lavoisier
(B)	Law of multiple proportions	(q) Gay Lussac
(C)	Law of conservation of mass	(r) Dalton
(D)	Law of gaseous volumes	(s) Joseph Proust

(a) A – (s), B – (r), C – (p), D – (q)

(b) A – (p), B – (r), C – (s), D – (q)

(c) A – (r), B – (p), C – (s), D – (q)

( d) A – (q), B – (s), C – (r), D – (p)

Q. 27 Match the columns

	Column-I	Column-II
(A)	C6H5NH2	(p) 84
(B)	C6H6	(q) 100
(C)	C6H12	(r) 93
(D)	CaCO3	(s) 78

(a) A – (p), B – (r), C – (q), D – (s)

(b) A – (r), B – (s), C – (p), D – (q)

(c) A – (r), B – (p), C – (q), D – (s)

( d) A – (r), B – (q), C – (s), D – (p)

Q. 28 Match the columns

	Column-I	Column-II
	((Number)	(Significant figures)
(A)	29900	(p) 2
(B)	290	(q) 1
(C)	1.23 × 1.331	(r) 4
(D)	20.00	(s) 3
(E)	2.783 – 1	(t) 5

(a) A – (r), B – (q), C – (t), D – (p), E – (s) (b) A – (t), B – (p), C – (s), D – (r), E – (q) (c) A – (p), B – (t), C – (s), D – (r), E – (q)

( d) A – (t), B – (s), C – (r), D – (q), E – (p)

Q. 29 Match the columns.

	Column-I	Column-II
	(Physical quantity)	(Unit)
(A)	Molarity	(p) mol
(B)	Mole fraction	(q) Unitless
(C)	Mole	(r) mol L–1
(D)	Molality	(s) mol kg–1

1. A – (r), B – (q), C – (s), D – (p)
2. A – (r), B – (p), C – (q), D – (s) (c) A – (r), B – (q), C – (p), D – (s)

( d) A – (q), B – (r), C – (p), D – (s)

Q. 30 Match the columns.

	Column-I	Column-II
(A)	88 g of CO2	(p) 0.25 mol
(B)	6.022 × 1023 molecules	(q) 2 mol of H2O
(C)	5.6 litres of O2 at STP	(r) 1 mol
(D)	96 g of O2	6.022 × 1023 molecules
(E)	1 mol of any gas	(t) 3 mol

(a) A – (q), B – (r), C – (p), D – (t), E – (s)

(b) A – (r), B – (q), C – (p), D – (t), E – (s)

(c) A – (q), B – (p), C – (r), D – (t), E – (s)

(d) A – (q), B – (r), C – (p), D – (s), E – (t)

Q. 31 Match the mass of elements given in Column I with the number of moles given in Column II and mark the appropriate choice. Choose the correct codes formt he options given below.

	Column-I	Column-II
(A)	28 g of He	(p) 2 moles
(B)	46 g of Na	(q) 7 moles
(C)	60 gm of Ca	(r) 1 mol
(D)	27 gm of Al	(s) 1.5 mole

1. A – (s), B – (r), C – (q), D – (p)
2. A – (p), B – (r), C – (q), D – (s)
3. A – (r), B – (q), C – (p), D – (s)
4. A – (q), B – (p), C – (s), D – (r)

Q. 32 Choose the correct combination

Element	Compound	Mixture
(A) Ammonia	Sodium	Air
(B) Water	Sugar	Aqueous sugar solution
(C) Hydrogen	Oxygen	Water
(D) Silver	Water	Air

(Q 33 TO Q 42)

Directions : Each of these questions contain two statements, Assertion and Reason. Each of these questions also has four alternative choices, only one of which is the correct answer. You have to select one of the codes (a), (b), (c) and (d) given below.

(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.

(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion

(c) Assertion is correct, reason is incorrect

(d) Assertion is incorrect, reason is correct.

(e) Assertion is incorrect, reason is also incorrect.

Q. 33 Assertion : The empirical mass of ethene is half of its molecular mass.

Reason : The empirical formula represents the simplest whole number ratio of various atoms present in a compound.

Q. 34 Assertion : Molality of a solution is temperature dependent concentration term

Reason : Molality refers to number of moles of solute dissolved in 1000 grams of solvent.

Q. 35 Assertion : Significant figures for 0.200 is 3 whereas for 200 it is 1.

Reason : Zero at the end or right of a number are significant provided they are not on the right side of the decimal point.

Q. 36 Assertion : 1.231 has three significant figures.

Reason : All numbers right to the decimal point are significant.

Q. 37 Assertion : One atomic mass unit is defined as one twelfth of the mass of one carbon – 12 atom.

Reason : Carbon-12 isotope is the most abundunt isotope of carbon and has been chosen as standard.

Q. 38 Assertion : Equal moles of different substances contain same number of constituent particles.

Reason : Equal weights of different substances contain the same number of constituent particles.

Q. 39 Assertion : Limiting reagent is one of the reactants in a reaction that decides the yield of the product.

Reason : Limiting reagent is left unreacted after the reaction.

Q. 40 Assertion : Formation of CO and CO₂ is in agreement with law of multiple proportion.

Reason : 12 grams of carbon combines with 16 grams of oxygen in CO but with 32 grams of oxygen in CO₂.

Q. 41 Assertion : Mole fration is dimensionless and temperature independent concentration term.

Reason : Mole fraction is the ratio of number of moles of a component in the solution to the total number of moles in the solution.

Q. 42 Assertion : Volume of a gas is inversely proportional to the number of moles of gas.

Reason : The ratio by volume of gaseous reactants and products is in agreement with their mole ratio.

Q. 43 n g of substance X reacts with m g of substance Y to form p g of substance R and q g of substance S. This reaction can be represented as, X + Y = R + S.

Establish correct relation among n, m, p and q. Also state the law that helps to find the relation.

Q. 44 In one experiment, 4g of H₂ combine with 32g of O₂ to form 36 g of H₂O. In another experiment, when 50g of H₂ combine with 400g of O₂ then 450g of H₂O is formed.

Above two experiments are in agreement of which law of chemical combination. State the law and explain the two experiments.

Q. 45 Irrespective of the source, pure sample, of water always yields 88.89% mass of oxygen and 11.11% mass of hydrogen. This is explained by which law of chemical combination? State the law also.

Q. 46 Two samples of lead oxide were separately reduced to metallic lead by heating in a current of hydrogen. The weight of lead from one oxide was half the weight of lead obtained from the other oxide.

Which law of chemical combination illustrates this data? Also state the law.

Q. 47 In compound A, 1.00g of nitrogen unites with 0.57g of oxygen. In compound B, 2.00g of nitrogen combines with 2.24g of oxygen. In compound C, 3.00g of nitrogen combines with 5.11g of oxygen.

These results obeyed which law of chemical combination? State the law.

Q. 48 Many countries use Fahrenheit scale for expressing temperature of atmosphere. If temperature in any such country is measured 41°F then

what is its value in celcius scale and would you expect hot or cold atmosphere in that country?

Q. 49 One kilogram of a sea water sample contains 6 mg of dissolved O₂. Find the concentration of O₂ in the sample in ppm.

Q. 50 What is the average atomic mass of bromine from the following data : (abundance is in %)

Isotope Mass Abundance

⁷⁹Br 78.9183361 50.69

⁸¹Br 80.916289 49.31

Q. 51 Arrange the following in the order of increasing mass (atomic mass: O = 16, Cu = 63, N = 14)

I. one atom of oxygen

II. one atom of nitrogen

III. 1 × 10^–10 mole of oxygen

IV. 1 × 10^–10 mole of copper

Q. 52 Arrange in increasing order of molarity with 25 gm each of NaOH, LiOH, Al(OH)₃, KOH, B(OH)₃ in same volume of water.

(atomic mass of Na=23, O=16, H=1, Li=7, Al=27, K=39, B=11)

Q. 53 Equal masses of H₂, O₂ and methane have been taken in a container of volume V at temperature 27 °C in identical conditions. Find the ratio of the volumes of gases H₂ : O₂ : methane in the container.

Q. 54 If Avogadro number N_A, is changed from 6.022 × 10²³ mol^–l to 6.022 × 10²⁰ mol^–l, how would this change the mass of one mole of carbon?

Q. 55 Which of the following quantities will have same dimensions of pressure? Explain with reason.

(force per unit volume) or (energy per unit volume)

Q. 56 25.3 g of sodium carbonate, Na₂CO₃ is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, calculate molar concentration of sodium ion and carbonate ion in the solution? ( atomic weight of Na=23, C=12, O=16)

Q. 57 What volume of oxygen gas (O₂) measured at 0°C and 1 atm, is needed to burn completely 1 L of propane gas (C₃H₈) measured under the same conditions?

Q. 58 How many moles of lead (II) chloride will be formed from a reaction between 6.5 g of PbO and 3.2 g HCl? ( atomic mass of Pb=207, O=16, H=1, Cl=35.5)

Q. 59 What will be the number of moles of oxygen in one litre of air containing 21% oxygen by volume, under standard conditions?

Q.60 Find the total number of valence electrons in terms of Avogadro’s number in 4.2 g of N₃^– ion. (atomic mass of N=14)

Q. 61 Boron has two stable isotopes, ^l0B(19%) and ¹¹B(81%). Calculate average atomic weight of boron in the periodic table.

Q. 62 The molecular weight of O₂ and SO₂ are 32 and 64 respectively. At 15°C and 150 mmHg pressure, one litre of O₂ contains ‘N’ molecules.

Calculate the number of molecules in two litres of SO₂ under the same conditions of temperature and pressure in terms of ‘N’.

Q. 63 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.

Q. 64 Calculate the concentration of nitic acid in moles per litre in a sample which has density 1.41 g/mL and the mass percent of nitic acid being 69%. (atomic mass of N=14, H=1 O=16)

Q. 65 Calculate the number of atoms in 4.25 g of NH_3. ( atomic mass of N=14, H=1)

Q. 66 What is the weight of oxygen required for the complete combustion of 2.8 kg of ethylene(C₂H₂)?

Q. 67 How are 0.5 mole Na₂CO₃, 0.5 molar Na₂CO₃ and 0.5 molal Na₂CO₃ are different from one another?

Q. 68 What will be molality of the solution containing 18.25 g of HCl in 500 g of water?

Q. 69 Calculate the molality of a solution of ethanol in water in which the mole fraction is 0.040.

Q. 70 If density of methanol (CH₃OH) is 0.793 kg/L, what is its volume needed for making 2.5 L of its 0.25M solution?

Q. 71 An organic compound contains carbon, hydrogen and oxygen. Its elemental analysis gave C=38.71% and H = 9.67%. Deduce the empirical formula of the compound.

Q. 72 Specific volume of cylindrical virus particle is 6.02 × 10^–2 cc/g whose radius and length are 7 Å and 10 Å respectively. If N_A = 6.02 × 10²³, find molecular weight of virus.

Q. 73 Suppose the elements X and Y combine to form two compounds XY₂ and X₃Y₂. When 0.1 mole of XY₂ weighs 10 g and 0.05 mole of X₃Y₂ weighs 9 g. Find the atomic weights of X and Y.

Q. 74 At STP, Find the density of CCl₄ vapours in g/L. (atomic weight of C=12, Cl=35.5)

Q. 75 The percentage of an element M is 53 in its oxide of molecular formula M₂O₃. Calculate atomic mass of M.

Q. 76 What is the mass of the precipitate formed when 50 mL of 16.9% (w/v) solution of AgNO₃ is mixed with 50 mL of 5.8% (w/v) NaCl solution? (Ag = 107.8, N = 14, O = 16, Na = 23,Cl = 35.5)

Q. 77 A mixture of gases contains H₂ and O₂ gases in the ratio of 1 : 4 (w/w). What is the molar ratio of the two gases in the mixture?

Q. 78 When 22.4 litres of H₂ gas is mixed with 11.2 litres of Cl₂ gas in a chamber at STP. How many moles of HCl gas will be produced?

Q. 79 1.0 g of magnesium is burnt with 0.56 g O₂ in a closed vessel. Which reactant is left in excess and how much? (At. wt. Mg = 24, O = 16)

Q. 80 10 g of hydrogen and 64 g of oxygen were filled in a steel vessel and exploded. How many moles of water will be produced in this reaction?

Q. 81 How many litres of CO₂ at STP will be obtained by the complete decomposition of 9.85 g of BaCO₃? (atomic weight of Ba=137, C=12, O=16)

Q. 82 How many grams of zinc required to produce 224 mL of H₂ at STP on treatment with dilute H₂SO₄? (atomic weight of Zn=65, H=1, S=32,O=16)

Q. 83 Calculate the number of gram molecules of oxygen in 6.02 × 10²⁴ molecules of carbon monoxide gas.

Q. 84 A metal oxide has the formula Z₂O₃ . It can be reduced by hydrogen gas to give free metal and water. 0.1596 g of the metal oxide requires 6 mg of hydrogen gas for complete reduction.

Deduce the atomic weight of the metal (Z).

Q. 85 20.0 kg of N_2(g) and 3.0 kg of H_2(g) are mixed to produce NH₃₍g₎. Find the amount of NH_3(g) formed.

Q. 86 20.0 kg of H₂(g) and 32 kg of O₂(g) are reacted to produce H₂O(l). What will be the amount of H₂O (l) formed after completion of reaction?

Q. 87 Liquid benzene (C₆H₆) burns in oxygen according to the equation

2C₆ H₆ (l) + 15O₂ (g ) →12CO ₂ ( g ) + 6H ₂O( g ).

How many litres of O₂ at STP are needed to complete the combustion of 39 g of liquid benzene? (Mol. wt. of O₂ = 32, C₆H₆ = 78)

Q. 88 What will be the mass of BaCO₃ produced when excess CO₂ is bubbled through a solution of 0.205 mol Ba(OH)₂ ? ( atomic mass of Ba=137, C=12, O=16)

Q.89 Fat is an important source of energy and water, this is important for the desert animals like camel which store fat in its hump and provide water and energy.

How many grams and moles of H₂O are produced from the combustion of fat C₅₇H₁₁₀O₆ from 450 gram of fat stored in hump of camel ?

C₅₇H₁₁₀O₆ + 163/2 O₂ → 57CO₂ + 55 H₂O

Q. 90 When 2.46 g of a hydrated salt ( MSO₄.xH₂O ) is completely dehydrated , 1.20 g of anhydrous salt is obtained . If the molecular weight of anhydrous salt is 120 g/mol, what is the value of x?

Q. 91 Haemoglobin contains 0.334% of iron by weight. The molecular weight of haemoglobin is approximately 67200.

How many iron atoms (Atomic weight of Fe is 56) are present in one molecule of haemoglobin?

Q. 92 When 1L of 0.1M H₂SO₄ solution is allowed to react with 1L of 0.1M NaOH solution, Calculate the amount of sodium sulphate formed and its molarity in the solution.

H₂SO₄ + 2NaOH → Na₂SO₄ + H₂O

Q. 93 What mass of CaCO₃ would be required to react completely with 25 mL of 0.75M HCl according to following equation?

CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O

(atomic mass of Ca=40, C=12, O=16, H=1, Cl=35.5)

Q. 94 How many grams of HCl will react with 5.0 g of manganese dioxide? The reaction between manganese dioxide and HCl is as follows:

MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O

(atomic mass of Mn=55, O=16, H=1, Cl=35.5)

Q. 95 Calculate the mass percentage of all constituent elements in calcium phosphate?

(atomic mass of Ca=40, P=31, O=16)

Q. 96 Read following paragraph and answer the questions that follow:

Solution is a homogeneous mixture of two or more substances. Concentration of a solution is expressed in many ways such as strength, molarity, molality, parts per million and mole fraction.

Some of these concentration terms are temperature dependent whereas some are temperature independent. If we know one concentration term of a solution, with the help of some other data, we can determine other concentration terms of the solution also. Physical state of a solution is same as physical state of the solvent in the solution.

(i) Can a solution be in solid state? If yes, give one example of it.

(ii) Write the expression showing relation between strength and molarity of solution.

(iii) Write any two concentration terms that are temperature dependent and two concentration terms that are temperature independent.

Q. 97 Read following paragraph and answer the questions that follow:

Molecular formula of a compound gives actual number of atoms of its constituent elements present in one molecule of the compound whereas empirical formula gives simple ratio of atoms of its constituent elements present in a molecule. We can deduce empirical formula of the compound from percentage composition of its constituent elements. Different compounds with same empirical formula have same percentage composition of its constituent elements, therefore to differentiate among such compounds, we need to know n-factor for the compound. Different compounds with same percentage composition of constituent elements and even with same n-factor are actually isomers.

(i)Write an expression to find n-factor for a compound.

(ii)Arrange formadehyde (HCHO) , acetic acid (CH₃COOH) and glucose(C₆H₁₂O₆) in increasing order of their n-factor.

(iii)If empirical formula of a compound is CH and its molar mass is 26 g/mol, Deduce molecular formula of the compound.

Q. 98 Read following paragraph and answer the questions that follow:

One of the most important aspects of a chemical equations that when it is written in the balanced form, it gives quantitative relationships between the various

reactants and products in terms of moles, masses molecules and volumes. This is called stoichiometry. The coefficients of the balanced chemical equation are called stoichiometric coefficients. These stoichiometric coefficients not only help to balance the equation but also tells about the quantity of reactants consumed or quantity of products formed in the reaction. Balancing a chemical equation is also must because every chemical change is in accordance with law of conservation of mass.

(i) What is stoichiometric coefficient of steam in following reaction?

Fe + H₂O → Fe₃O₄ + H₂

(ii)How many moles of Fe will react with one mole of steam in above reaction?

(iii) Prove that following reaction is in accordance with law of conservation of mass: (atomic mass of Ca=40, C=12, O=16, H=1, Cl=35.5)

CaCO₃ + 2HCl →CaCl₂ + CO₂ + H₂O

Q. 99 Read following paragraph and answer the questions that follow:

Quite often, one of the reactants is present in large amount than the other as required according to the balanced equations. The amount of the product formed then depends upon the reactant that has reacted completely. This reactant which consumes completely in the reaction is called as limiting reagent. The reactant which is not consumed completely in the reaction is called excess reactant as some quantity of this reactant is left unreacted after the reaction. For example 18 grams of carbon are burnt in 32 grams of dioxygen gas and reaction occurs as follows: C + O₂ → CO₂

(i)Which is limiting reagent in this reaction?

(ii)How many grams of carbon dioxide will form in the reaction?

(iii)Which is excess reactant in the reaction ? How many moles of it will be left unused after the reaction?

Q. 100 Read following paragraph and answer the questions that follow:

If the average value of different measurements is close to the correct value , the measurement is said to be accurate ( the individual measurements may not be close to each other.

If the values of different measurements are close to each other and hence close to their average value, the measurement is said to be precise ( the average value of different measurements may not be close to the correct value). The precision depends upon the measuring device as well as the skill of the operator.

For example, suppose the actual length of the room is 10.5 m. Four different people report the result of their five measurements as follow:

Measurement (m)	SET-1	SET-2	SET-3	SET-4	SET-5	Average (m)
Person-A	10.3	10.4	10.5	10.6	10.7	10.5
Person-B	10.0	10.1	10.2	10.3	10.4	10.2
Person-C	10.1	10.3	10.5	10.7	10.9	10.5
Person-D	10.0	10.7	10.9	11.1	11.3	10.8

(i) Which person has good precision as well as good accuracy?

(ii) Which person has precision and accuracy both poor?

(iii) Which person has good accuracy just by chance but poor precision?

(iv) Which person has poor accuracy but good precision?