Chapter 1

Calculate the molarity of water if its density is \(1000 \mathrm{~kg} / \mathrm{m}^{3}\). [2003 - 2 Marks]

\(\mathrm{NaClO}_{3}\) is used, even in spacecrafts, to produce \(\mathrm{O}_{2}\). The daily consumption of pure \(\mathrm{O}_{2}\) by a person is \(492 \mathrm{~L}\) at 1 atm, \(300 \mathrm{~K}\). How much amount of \(\mathrm{NaClO}_{3}\), in grams, is required to produce \(\mathrm{O}_{2}\) for the daily consumption of a person at \(1 \mathrm{~atm}, 300 \mathrm{~K}\) ? \(\mathrm{NaClO}_{3}(\mathrm{~s})+\mathrm{Fe}(\mathrm{s}) \rightarrow \mathrm{O}_{2}(\mathrm{~g})+\mathrm{NaCl}(\mathrm{s})+\mathrm{FeO}(\mathrm{s}) \mathrm{R}=0 . \overline{082 \mathrm{Latm}} \mathrm{mol}^{-1} \mathrm{~K}^{-1}\) [Main Jan. 08, 2020 (II)]

In the chemical reaction between stoichiometric quantities of \(\mathrm{KMnO}_{4}\) and KI in weakly basic solution, what is the number of moles of \(\mathrm{I}_{2}\) released for 4 moles of \(\mathrm{KMnO}_{4}\) consumed? [Adv. 2020]

A compound contains 28 percent of nitrogen and 72 percent of metal by weight. 3 atoms of metal combine with 2 atoms of \(\mathrm{N}\). Find the atomic weight of metal.

The ammonia prepared by treating ammonium sulphate with calcium hydroxide is completely used by \(\mathrm{NiCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\) to form a stable coordination compound. Assume that both the reactions are \(100 \%\) complete. If \(1584 \mathrm{~g}\) of ammonium sulphate and \(952 \mathrm{~g}\) of \(\mathrm{NiCl}_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\) are used in the preparation, the combined weight (in grams) of gypsum and the nickel-ammonia coordination compound thus produced is(Atomic weights in \(\mathrm{g} \mathrm{mol}^{-1}\) : \(\mathrm{H}=1, \mathrm{~N}=14, \mathrm{O}=16, \mathrm{~S}=32, \mathrm{Cl}=35.5, \mathrm{Ca}=\) \(40, \mathrm{Ni}=59\) )

Galena (an ore) is partially oxidized by passing air through it at high temperature. After some time, the passage of air is stopped, but the heating is continued in a closed furnace such that the contents undergo self- reduction. The weight (in \(\mathrm{kg}\) ) of Pb produced per \(\mathrm{kg}\) of \(\mathrm{O}_{2}\) consumed is (Atomic weights in \(\mathrm{g} \mathrm{mol}^{-1}: \mathrm{O}=16, \mathrm{~S}=32, \mathrm{~Pb}=207\) ) [Adv. 2018]

One gram of commercial \(\mathrm{AgNO}_{3}\) is dissolved in \(50 \mathrm{~mL}\). of water. It is treated with \(50 \mathrm{~mL}\). of a KI solution. The silver iodide thus precipitated is filtered off. Excess of KI in the filterate is titrated with \((\mathrm{M} / 10) \mathrm{KIO}_{3}\) solution in presence of \(6 \mathrm{M} \mathrm{HCl}\) till all I- ions are converted into ICl. It requires \(50 \mathrm{~mL}\). of \((\mathrm{M} / 10) \mathrm{KIO}_{3}\) solution. \(20 \mathrm{~mL}\). of the same stock solution of KI requires \(30 \mathrm{~mL}\). of \((\mathrm{M} / 10) \mathrm{KlO}_{3}\) under similar conditions. Calculate the percentage of \(\mathrm{AgNO}_{3}\) in the sample. (Reaction: \(\left.\mathrm{KIO}_{3}+2 \mathrm{KI}+6 \mathrm{HCl} \rightarrow 3 \mathrm{ICl}+3 \mathrm{KCl}+3 \mathrm{H}_{2} \mathrm{O}\right)\)

A plant virus is found to consist of uniform cylindrical particles of \(150 \AA\) in diameter and \(5000 \AA\) long. The specific volume of the virus is \(0.75 \mathrm{~cm}^{3} / \mathrm{g}\). If the virus is considered to be a single particle, find its molar mass.

(a) One litre of a sample of hard water contains \(1 \mathrm{mg}\) of \(\mathrm{CaCl}_{2}\) and 1 \(\mathrm{mg}\) of \(\mathrm{MgCl}_{2}\). Find the total hardness in terms of parts of \(\mathrm{CaCO}_{3}\) per \(10^{6}\) parts of water by weight. (b) A sample of hard water contains \(20 \mathrm{mg}\) of \(\mathrm{Ca}^{++}\)ions per litre. How many milli-equivalent of \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) would be required to soften 1 litre of the sample? (c) \(1 \mathrm{~g}\) of \(\mathrm{Mg}\) is burnt in a closed vessel which contains \(0.5 \mathrm{~g}\) of \(\mathrm{O}_{2}\). (i) Which reactant is left in excess? (ii) Find the weight of the excess reactants? (iii) How may milliliters of \(0.5 \mathrm{~N} \mathrm{H}_{2} \mathrm{SO}_{4}\) will dissolve the residue in the vessel.

Calculate the molality of 1 litre solution of \(93 \% \mathrm{H}_{2} \mathrm{SO}_{4}\) (weight/volume). The density of the solution is \(1.84 \mathrm{~g} / \mathrm{mL}\). [1990 - 1 Marks]

A hydrocarbon contains \(10.5 \mathrm{~g}\) of carbon per gram of hydrogen. 1 litre of the vapour of the hydrocarbon at \(127^{\circ} \mathrm{C}\) and 1 atmosphere pressure weighs \(2.8 \mathrm{~g}\). Find the molecular formula.

Find (i) The total number of neutrons and (ii) The total mass of neutron in \(7 \mathrm{mg}\) of \({ }^{14} \mathrm{C}\). (Assume that mass of neutron = mass of hydrogen atom)

Hydroxylamine reduces iron (III) according to the equation: \(2 \mathrm{NH}_{2} \mathrm{OH}+4 \mathrm{Fe}^{3+} \rightarrow \mathrm{N}_{2} \mathrm{O}(\mathrm{g}) \uparrow+\mathrm{H}_{2} \mathrm{O}+4 \mathrm{Fe}^{2+}+4 \mathrm{H}^{+}\) Iron (II) thus produced is estimated by titration with a standard permanganate solution. The reaction is : $$ \mathrm{MnO}_{4}^{-}+5 \mathrm{Fe}^{2+}+8 \mathrm{H}^{+} \rightarrow \mathrm{Mn}^{2+}+5 \mathrm{Fe}^{3+}+4 \mathrm{H}_{2} \mathrm{O} $$ A \(10 \mathrm{~mL}\). sample of hydroxylamine solution was diluted to 1 litre. \(50 \mathrm{~mL}\). of this diluted solution was boiled with an excess of iron (III) solution. The resulting solution required \(12 \mathrm{~mL}\). of \(0.02 \mathrm{M} \mathrm{KMnO}_{4}\) solution for complete oxidation of iron (II). Calculate the weight of hydroxylamine in one litre of the original solution. \((\mathrm{H}=1, \mathrm{~N}=14, \mathrm{O}\) \(=16, \mathrm{~K}=39, \mathrm{Mn}=55, \mathrm{Fe}=56)\) [1982 - 4 Marks]

\(4.215 \mathrm{~g}\) of a metallic carbonate was heated in a hard glass tube and the \(\mathrm{CO}_{2}\) evolved was found to measure \(1336 \mathrm{~mL}\) at \(27^{\circ} \mathrm{C}\) and \(700 \mathrm{~mm}\) pressure. What is the equivalent weight of the metal? [1979

What weight of \(\mathrm{AgCl}\) will be precipitated when a solution containing \(4.77 \mathrm{~g}\) of \(\mathrm{NaCl}\) is added to a solution of \(5.77 \mathrm{~g}\) of \(\mathrm{AgNO}_{3} ?\) [1978]

Igniting \(\mathrm{MnO}_{2}\) converts it quantitatively to \(\mathrm{Mn}_{3} \mathrm{O}_{4}\). A sample of pyrolusite is of the following composition: \(\mathrm{MnO}_{2} 80 \%, \mathrm{SiO}_{2}\) andother inert constituents \(15 \%\), rest being water. The sample is ignited in air to constant weight. What is the percentage of \(\mathrm{Mn}\) in the ignited sample? \([1978]\) \([\mathrm{O}=16, \mathrm{Mn}=54.9]\)

\(3 \mathrm{~g}\) of a salt of molecular weight 30 is dissolved in \(250 \mathrm{~g}\) of water. The molality of the solution is \(\ldots \ldots \ldots \ldots . . .\) [1983-1 Mark]

Read the following statement and explanation and answer as per the options given below: Statement(S) : In the titration of \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) with HCl using methyl orange indicator, the volume required at the equivalence point is twice that of the acid required using phenolphthalein indicator. explanation(E) : Two moles of \(\mathrm{HCl}\) are required for the complete neutralization of one mole of \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) [1991 - 2 Marks] (a) Both \(\mathrm{S}\) and \(\mathrm{E}\) are true, and \(\mathrm{E}\) is the correct explanation of \(\mathrm{S}\). (b) Both \(S\) and \(E\) are true, but \(E\) is not the correct explanation of \(S\). (c) \(\mathrm{S}\) is true but \(\mathrm{E}\) is false. (d) \(\mathrm{S}\) is false but \(\mathrm{E}\) is true.

Hydrogen peroxide solution ( \(20 \mathrm{~mL}\) ) reacts quantitatively with a solution of \(\mathrm{KMnO}_{4}\) ( \(20 \mathrm{~mL}\) ) acidified with dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\). The same volume of the \(\mathrm{KMnO}_{4}\) solution is just decolourised by \(10 \mathrm{~mL}\) of \(\mathrm{MnSO}_{4}\) in neutral medium simultaneously forming a dark brown precipitate of hydrated \(\mathrm{MnO}_{2}\). The brown precipitate is dissolved in \(10 \mathrm{~mL}\) of \(0.2 \mathrm{M}\) sodium oxalate under boiling condition in the presence of dilute \(\mathrm{H}_{2} \mathrm{SO}_{4} .\) Write the balanced equations involved in the reactions and calculate the molarity of \(\mathrm{H}_{2} \mathrm{O}_{2}\). [2001-5 Marks]

An aqueous solution containing \(0.10 \mathrm{~g} \mathrm{KIO}_{3}\) (formula weight \(=214.0\) ) was treated with an excess of KI solution. The solution was acidified with HCl. The liberated \(\mathrm{I}_{2}\) consumed \(45.0 \mathrm{~mL}\) of thiosulphate solution to decolourise the blue starch-iodine complex. Calculate the molarity of the sodium thiosulphate solution. [1998-5 Marks]

A \(3.00 \mathrm{~g}\) sample containing \(\mathrm{Fe}_{3} \mathrm{O}_{4}, \mathrm{Fe}_{2} \mathrm{O}_{3}\) and an inert impure substance, is treated with excess of KI solution in presence of dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\). The entire iron is converted into \(\mathrm{Fe}^{2+}\) along with the liberation of iodine. The resulting solution is diluted to \(100 \mathrm{~mL}\). A \(20 \mathrm{~mL}\) of the diluted solution requires \(11.0 \mathrm{~mL}\) of \(0.5 \mathrm{M} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}\) solution to reduce the iodine present. A \(50 \mathrm{~mL}\) of the diluted solution, after complete extraction of the iodine requires \(12.80 \mathrm{~mL}\) of \(0.25 \mathrm{M} \mathrm{KMnO}_{4}\) solution in dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\) medium for the oxidation of \(\mathrm{Fe}^{2+}\). Calculate the percentages of \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) and \(\mathrm{Fe}_{3} \mathrm{O}_{4}\) in the original sample. |1996 - 5 Marksl

\(8.0575 \times 10^{-2} \mathrm{~kg}\) of Glauber's salt is dissolved in water to obtain 1 \(\mathrm{dm}^{3}\) of a solution of density \(1077.2 \mathrm{~kg} \mathrm{~m}^{3}\). Calculate the molarity, molality and mole fraction of \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) in the solution. [1994 - 3 Marks]

Upon mixing \(45.0 \mathrm{~mL}\). of \(0.25 \mathrm{M}\) lead nitrate solution with \(25.0 \mathrm{~mL}\) of \(0.10 \mathrm{M}\) chromic sulphate solution, precipitation of lead sulphate takes place. How many moles of lead sulphate are formed? Also, calculate the molar concentrations of the species left behind in the final solution. Assume that lead sulphate is completely insoluble. [1993 - 3 Marks]

A \(2.0 \mathrm{~g}\) sample of a mixture containing sodium carbonate, sodium bicarbonate and sodium sulphate is gently heated till the evolution of \(\mathrm{CO}_{2}\) ceases. The volume of \(\mathrm{CO}_{2}\) at \(750 \mathrm{~mm}\) Hg pressure and at \(298 \mathrm{~K}\) is measured to be \(123.9 \mathrm{~mL}\). A \(1.5 \mathrm{~g}\) of the same sample requires 150 mL. of \((\mathrm{M} / 10) \mathrm{HCl}\) for complete neutralisation. Calculate the \(\%\) composition of the components of the mixture. $$ \text { Page } 36,1,773-Q+\quad[1992-5 \text { Marks }] $$

A solution of \(0.2 \mathrm{~g}\) of a compound containing \(\mathrm{Cu}^{2+}\) and \(\mathrm{C}_{2} \mathrm{O}_{4}^{2-}\) ions on titration with \(0.02 \mathrm{M} \mathrm{KMnO}_{4}\) in presence of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) consumes \(22.6\) \(\mathrm{mL}\). of the oxidant. The resultant solution is neutralized with \(\mathrm{Na}_{2} \mathrm{CO}_{3}\), acidified with dil. acetic acid and treated with excess KI. The liberated iodine requires \(11.3 \mathrm{~mL}\) of \(0.05 \mathrm{M} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}\) solution for complete reduction. Find out the molar ratio of \(\mathrm{Cu}^{2+}\) to \(\mathrm{C}_{2} \mathrm{O}_{4}^{2-}\) in the compound. Write down the balanced redox reactions involved in the above titrations. [1991 - 5 Marks]

A mixture of \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) (oxalic acid) and \(\mathrm{NaHC}_{2} \mathrm{O}_{4}\) weighing \(2.02 \mathrm{~g}\) was dissolved in water and solution made upto one litre. Ten millilitres of the solution required \(3.0 \mathrm{~mL}\). of \(0.1 \mathrm{~N}\) sodium hydroxide solution for complete neutralization. In another experiment, \(10.0 \mathrm{~mL}\). of the same solution, in hot dilute sulphuric acid medium. require \(4.0 \mathrm{~mL}\). of \(0.1\) N potassium permanganate solution for complete reaction. Calculate the amount of \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\) and \(\mathrm{NaHC}_{2} \mathrm{O}_{4}\) in the mixture. [1990 - 5 Marks]

A solid mixture \((5.0 \mathrm{~g})\) consisting of lead nitrate and sodium nitrate was heated below \(600^{\circ} \mathrm{C}\) until the weight of the residue was constant. If the loss in weight is \(28.0\) per cent, find the amount of lead nitrate and sodium nitrate in the mixture. [1990-4 Marks]

A sugar syrup of weight \(214.2 \mathrm{~g}\) contains \(34.2 \mathrm{~g}\) of sugar \(\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)\). Calculate : (i) molal concentration and (ii) mole fraction of sugar in the syrup.

(i) What is the weight of sodium bromate and molarity of solution necessary to prepare \(85.5 \mathrm{~mL}\) of \(0.672 \mathrm{~N}\) solution when the halfcell reaction is $$ \mathrm{BrO}_{3}^{-}+6 \mathrm{H}^{+}+6 \mathrm{e}^{-} \rightarrow \mathrm{Br}^{-}+3 \mathrm{H}_{2} \mathrm{O} $$ (ii) What would be the weight as well as molarity if the half-cell reaction is : $$ 2 \mathrm{BrO}_{3}^{-}+12 \mathrm{H}^{+}+10 \mathrm{e}^{-} \rightarrow \mathrm{Br}_{2}+6 \mathrm{H}_{2} \mathrm{O} $$ [1987 - 5 Marks]

Five \(\mathrm{mL}\) of \(8 \mathrm{~N}\) nitric acid, \(4.8 \mathrm{~mL}\) of \(5 \mathrm{~N}\) hydrochloric acid and a certain volume of \(17 \mathrm{M}\) sulphuric acid are mixed together and made upto 2litre. Thirty \(\mathrm{mL}\). of this acid mixture exactly neutralise \(42.9 \mathrm{~mL}\) of sodium carbonate solution containing one gram of \(\mathrm{Na}_{2} \mathrm{CO}_{3} .10 \mathrm{H}_{2} \mathrm{O}\) in \(100 \mathrm{~mL}\). of water. Calculate the amount in gram of the sulphate ions in solution. [1985 - 4 Marks]

\(4.08 \mathrm{~g}\) of a mixture of \(\mathrm{BaO}\) and an unknown carbonate \(\mathrm{MCO}_{3}\) was heated strongly. The residue weighed \(3.64 \mathrm{~g}\). This was dissolved in \(100 \mathrm{~mL}\) of \(1 \mathrm{~N} \mathrm{HCl}\). The excess acid required \(16 \mathrm{~mL}\) of \(2.5 \mathrm{~N} \mathrm{NaOH}\) solution for complete neutralization. Identify the metal \(M . \quad\) [1983 - 4 Marks] (At. wt. \(\mathrm{H}=1, \mathrm{C}=12, \mathrm{O}=16, \mathrm{Cl}=35.5, \mathrm{Ba}=138\) )

(i) A sample of \(\mathrm{MnSO}_{4} \cdot 4 \mathrm{H}_{2} \mathrm{O}\) is strongly heated in air. The residue is \(\mathrm{Mn}_{3} \mathrm{O}_{4}\)(ii) The residue is dissolved in \(100 \mathrm{~mL}\) of \(0.1 \mathrm{~N} \mathrm{FeSO}_{4}\) containing dilute \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (iii) The solution reacts completely with \(50 \mathrm{~mL}\) of \(\mathrm{KMnO}_{4}\) solution. (iv) \(25 \mathrm{~mL}\) of the \(\mathrm{KMnO}_{4}\) solution used in step (iii) requires \(30 \mathrm{~mL}\) of \(0.1\) N \(\mathrm{FeSO}_{4}\) solution for complete reaction. Find the amount of \(\mathrm{MnSO}_{4} \cdot 4 \mathrm{H}_{2} \mathrm{O}\) present in the sample. [1980]

A mixture contains \(\mathrm{NaCl}\) and unknown chloride MCl. (i) \(1 \mathrm{~g}\) of this is dissolved in water. Excess of acidified \(\mathrm{AgNO}_{3}\) solution is added to it. \(2.567 \mathrm{~g}\) of white ppt. is formed. (ii) \(1 \mathrm{~g}\) of original mixture is heated to \(300^{\circ} \mathrm{C}\). Some vapours come out which are absorbed in acidified \(\mathrm{AgNO}_{3}\) solution, \(1.341 \mathrm{~g}\) of white precipitate was obtained. Find the molecular weight of unknown chloride. [1980]

\(5 \mathrm{~mL}\) of a gas containing only carbon and hydrogen were mixed with an excess of oxygen \((30 \mathrm{~mL})\) and the mixture exploded by means of an electric spark. After the explosion, the volume of the mixed gases remaining was \(25 \mathrm{~mL}\). On adding a concentrated solution of potassium hydroxide, the volume further diminished to \(15 \mathrm{~mL}\) of the residual gas being pure oxygen. All volumes have been reduced to N. T.P. Calculate the molecular formula of the hydrocarbon gas. \([1979]\)

One gram of an alloy of aluminium and magnesium when treated with excess of dil. HCl forms magnesium chloride, aluminium chloride and hydrogen. The evolved hydrogen, collected over mercury at \(0^{\circ} \mathrm{C}\) has a volume of \(1.20\) litres at \(0.92\) atm. pressure. Calculate the composition of the alloy. \([\mathrm{H}=1, \mathrm{Mg}=24, \mathrm{Al}=27]\)