Some Basic Concepts of Chemistry
On complete combustion, $0.492 \mathrm{~g}$ of an organic compound gave $0.792 \mathrm{~g}$ of $\mathrm{CO}_{2}$. The % of carbon in the organic compound is ___________ (Nearest integer)
Explanation:
$ \begin{aligned} & =\frac{12}{44} \times 0.792=0.216 \\\\ & \% \text { of } C \text { in compound }=\frac{0.216}{0.492} \times 100 \\\\ & =43.90 \% \end{aligned} $
The strength of 50 volume solution of hydrogen peroxide is ______ $\mathrm{g} / \mathrm{L}$ (Nearest integer).
Given:Molar mass of $\mathrm{H}_{2} \mathrm{O}_{2}$ is $34 \mathrm{~g} \mathrm{~mol}^{-1}$
Molar volume of gas at $\mathrm{STP}=22.7 \mathrm{~L}$
Explanation:
$\mathrm{H_2O_2\longrightarrow H_2O+\frac{1}{2}O_2}$
$\frac{50}{22.7}$
$\therefore$ Moles of $\mathrm{H_2O_2}$ in solution $=\frac{50}{22.7}\times2$
$\therefore$ Strength $=\frac{\frac{50\times2}{22.7}\times34}{1}=149.78\approx150$
Some amount of dichloromethane $\left(\mathrm{CH}_{2} \mathrm{Cl}_{2}\right)$ is added to $671.141 \mathrm{~mL}$ of chloroform $\left(\mathrm{CHCl}_{3}\right)$ to prepare $2.6 \times 10^{-3} \mathrm{M}$ solution of $\mathrm{CH}_{2} \mathrm{Cl}_{2}(\mathrm{DCM})$. The concentration of $\mathrm{DCM}$ is ___________ ppm (by mass).
Given :
atomic mass : C = 12
H = 1
Cl = 35.5
density of $\mathrm{CHCl}_{3}=1.49 \mathrm{~g} \mathrm{~cm}^{-3}$
Explanation:
Mass of $\mathrm{CHCl_3=671.141\times1.49=1000}$ gm
$2.6 \times {10^{ - 3}} = {{moles\,of\,C{H_2}C{l_2}} \over {0.671141}}$
$\Rightarrow$ moles of $C{H_2}C{l_2} = 1.74496 \times {10^{ - 3}}$
mass of $C{H_2}C{l_2} = 148.32 \times {10^{ - 3}}$ gm
Composition of $C{H_2}C{l_2} = {{148.32 \times {{10}^{ - 3}}} \over {1000}} \times {10^6}$
= 148.32 ppm
$\approx$ 148
The volume of HCl, containing 73 g L$^{-1}$, required to completely neutralise NaOH obtained by reacting 0.69 g of metallic sodium with water, is __________ mL. (Nearest Integer)
(Given : molar masses of Na, Cl, O, H, are 23, 35.5, 16 and 1 g mol$^{-1}$ respectively.)
Explanation:
$\mathrm{\mathop {Na + {H_2}O}\limits_{0.69\,g} \to \mathop {NaOH + {1 \over 2}{H_2}}\limits_{0.03\,moles}} $
= 0.03 moles
$\therefore 0.03=2\times\mathrm{V}$
$\mathrm{V=\frac{0.03}{2}L}$
= 15 mL
When 0.01 mol of an organic compound containing 60% carbon was burnt completely, 4.4 g of CO$_2$ was produced. The molar mass of compound is _____________ g mol$^{-1}$ (Nearest integer).
Explanation:
Number of moles of $C{O_2} = {{4.4} \over {44}} = 0.1$
$\therefore$ Number of moles of C in 1 mole of compound = 10
$\therefore$ $120 = {{60} \over {100}} \times (x)$ [where x is molar mass of OC]
Molar mass = 200 g mol$^{-1}$
Number of hydrogen atoms per molecule of a hydrocarbon A having 85.8% carbon is __________
(Given : Molar mass of A = 84 g mol$^{-1}$)
Explanation:
Mass of carbon in $1 \mathrm{~mol}$ of $(A)=\frac{85.8}{100} \times 84$
$ =72 ~\mathrm{gm} $
Mass of hydrogen in $1 \mathrm{~mol}$ of $(A)=12 ~\mathrm{gm}$
$\therefore$ Number of $\mathrm{H}$-atoms in a molecule of $(\mathrm{A})=12$.
In sulphur estimation, 0.471 g of an organic compound gave 1.4439 g of barium sulphate. The percentage of sulphur in the compound is ____________ (Nearest Integer)
(Given : Atomic mass Ba: 137 u, S: 32 u, O: 16 u)
Explanation:
The number of units, which are used to express concentration of solutions from the following is _________
Mass percent, Mole, Mole fraction, Molarity, ppm, Molality
Explanation:
When $\mathrm{Fe_{0.93}O}$ is heated in presence of oxygen, it converts to $\mathrm{Fe_2O_3}$. The number of correct statement/s from the following is ________
A. The equivalent weight of $\mathrm{Fe_{0.93}O}$ is ${{\mathrm{Molecular\,weight}} \over {0.79}}$
B. The number of moles of Fe$^{2+}$ and Fe$^{3+}$ in 1 mole of $\mathrm{Fe_{0.93}O}$ is 0.79 and 0.14 respectively
C. $\mathrm{Fe_{0.93}O}$ is metal deficient with lattice comprising of cubic closed packed arrangement of O$^{2-}$ ions
D. The % composition of Fe$^{2+}$ and Fe$^{3+}$ in $\mathrm{Fe_{0.93}O}$ is 85% and 15% respectively
Explanation:
According to the charge neutrality,
$ \begin{aligned} & 2 x+3(0.93-x)=2 \Rightarrow 2 x-3 x+2.79=2 \Rightarrow x=0.79 \\\\ & \mathrm{Fe}^{2+} \text { ion }=x=0.79 \\\\ & \mathrm{Fe}^{3+} \text { ion }=0.93-x=0.93-0.79=0.14 \\\\ & \% \text { of } \mathrm{Fe}^{2+} \text { ion }=\frac{0.79}{0.93} \times 100=84.95 \% \approx 85 \% \\\\ & \% \text { of } \mathrm{Fe}^{3+} \text { ion }=\frac{0.14}{0.93} \times 100=15.05 \% \end{aligned} $
As it is a metal deficiency defect,
so, 1 mol of $\mathrm{Fe}_{0.93} \mathrm{O}$ contains $1 \mathrm{~mol}$ of oxide ions and $0.93 \mathrm{~mol}$ of iron ions as $\mathrm{Fe}^{2+}$ and $\mathrm{Fe}^{3+}$.
So, moles of $\mathrm{Fe}^{2+}=0.79$
and moles of $\mathrm{Fe}^{3+}=0.14$
$ \text { The equivalent weight }=\frac{\text { Molecular weight }}{n \text {-factor }} $
$F{e^{2 + }} \to F{e^{3 + }} + {e^ - }$
For one $\mathrm{Fe}^{2+}, n$-factor $=1$
$\therefore $ For $0.79 \,\mathrm{Fe}^{2+}, n$-factor $=0.79$
Out of $0.93 \mathrm{~mol}$, there are $0.79 \mathrm{~mol} \,\mathrm{Fe}^{2+}$ ions are present.
5 g of NaOH was dissolved in deionized water to prepare a 450 mL stock solution. What volume (in mL) of this solution would be required to prepare 500 mL of 0.1 M solution? _____________
Given : Molar Mass of Na, O and H is 23, 16 and 1 g mol$^{-1}$ respectively
Explanation:
$\Rightarrow M \times V=500 \times .1$
$\Rightarrow \frac{5}{40} \times \frac{1000}{450} \times V=500 \times 0.1$
$\mathrm{V}=180 \mathrm{~mL}$
Consider the reaction
$4 \mathrm{HNO}_{3}(1)+3 \mathrm{KCl}(\mathrm{s}) \rightarrow \mathrm{Cl}_{2}(\mathrm{~g})+\mathrm{NOCl}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+3 \mathrm{KNO}_{3}(\mathrm{~s})$
The amount of $\mathrm{HNO}_{3}$ required to produce $110.0 \mathrm{~g}$ of $\mathrm{KNO}_{3}$ is
(Given: Atomic masses of $\mathrm{H}, \mathrm{O}, \mathrm{N}$ and $\mathrm{K}$ are $1,16,14$ and 39, respectively.)
$ \begin{aligned} &\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g})+400 \mathrm{~kJ} \\ &\mathrm{C}(\mathrm{s})+\frac{1}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}(\mathrm{g})+100 \mathrm{~kJ} \end{aligned} $
When coal of purity 60% is allowed to burn in presence of insufficient oxygen, 60% of carbon is converted into 'CO' and the remaining is converted into '$\mathrm{CO}_{2}$'. The heat generated when $0.6 \mathrm{~kg}$ of coal is burnt is _________.
$ \mathrm{N}_{2(\mathrm{~g})}+3 \mathrm{H}_{2(\mathrm{~g})} \rightleftharpoons 2 \mathrm{NH}_{3(\mathrm{~g})} $
$20 \mathrm{~g} \quad ~~~5 \mathrm{~g}$
Consider the above reaction, the limiting reagent of the reaction and number of moles of $\mathrm{NH}_{3}$ formed respectively are :
$250 \mathrm{~g}$ solution of $\mathrm{D}$-glucose in water contains $10.8 \%$ of carbon by weight. The molality of the solution is nearest to
(Given: Atomic Weights are, $\mathrm{H}, 1 \,\mathrm{u} ; \mathrm{C}, 12 \,\mathrm{u} ; \mathrm{O}, 16 \,\mathrm{u}$)
In Carius method of estimation of halogen, $0.45 \mathrm{~g}$ of an organic compound gave $0.36 \mathrm{~g}$ of $\mathrm{AgBr}$. Find out the percentage of bromine in the compound.
(Molar masses : $\mathrm{AgBr}=188 \mathrm{~g} \mathrm{~mol}^{-1} ; \mathrm{Br}=80 \mathrm{~g} \mathrm{~mol}^{-1}$)
Hemoglobin contains $0.34 \%$ of iron by mass. The number of Fe atoms in $3.3 \mathrm{~g}$ of hemoglobin is
(Given: Atomic mass of Fe is $56 \,\mathrm{u}, \mathrm{N}_{\mathrm{A}}=6.022 \times 10^{23} \mathrm{~mol}^{-1}$.)
$\mathrm{SO}_{2} \mathrm{Cl}_{2}$ on reaction with excess of water results into acidic mixture
$\mathrm{SO}_{2} \mathrm{Cl}_{2}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{H}_{2} \mathrm{SO}_{4}+2 \mathrm{HCl}$
16 moles of $\mathrm{NaOH}$ is required for the complete neutralisation of the resultant acidic mixture. The number of moles of $\mathrm{SO}_{2} \mathrm{Cl}_{2}$ used is :
Using the rules for significant figures, the correct answer for the expression ${{0.02858 \times 0.112} \over {0.5702}}$ will be
Production of iron in blast furnace follows the following equation
Fe3O4(s) + 4CO(g) $\to$ 3Fe(l) + 4CO2(g)
when 4.640 kg of Fe3O4 and 2.520 kg of CO are allowed to react then the amount of iron (in g) produced is :
[Given : Molar Atomic mass (g mol$-$1) : Fe = 56, Molar Atomic mass (g mol$-$1) : O = 16, Molar Atomic mass (g mol$-$1) : C = 12]
Compound A contains 8.7% Hydrogen, 74% Carbon and 17.3% Nitrogen. The molecular formula of the compound is,
Given : Atomic masses of C, H and N are 12, 1 and 14 amu respectively.
The molar mass of the compound A is 162 g mol$-$1.
A commercially sold conc. HCl is 35% HCl by mass. If the density of this commercial acid is 1.46 g/mL, the molarity of this solution is:
(Atomic mass : Cl = 35.5 amu, H = 1 amu)
120 g of an organic compound that contains only carbon and hydrogen gives 330 g of CO2 and 270 g of water on complete combustion. The percentage of carbon and hydrogen, respectively are
If a rocket runs on a fuel (C15H30) and liquid oxygen, the weight of oxygen required and CO2 released for every litre of fuel respectively are :
(Given : density of the fuel is 0.756 g/mL)
A 1.84 mg sample of polyhydric alcoholic compound 'X' of molar mass 92.0 g/mol gave 1.344 mL of $\mathrm{H}_{2}$ gas at STP. The number of alcoholic hydrogens present in compound 'X' is ________.
Explanation:
STP conditions define the volume of 1 mole of any gas as $22.4$ liters or $22400$ mL. The volume of hydrogen gas evolved here is $1.344$ mL, so we can calculate the number of moles of hydrogen gas ($H_2$) using the formula:
$n = \frac{V}{V_m}$
where:
- $n$ is the number of moles,
- $V$ is the volume of the gas, and
- $V_m$ is the molar volume of the gas.
Substituting in the given values:
$n = \frac{1.344 \text{ mL}}{22400 \text{ mL/mol}} = 5.995 \times 10^{-5} \text{ mol}$
Each molecule of $H_2$ contains $2$ atoms of hydrogen. Therefore, the number of moles of hydrogen atoms is twice the number of moles of hydrogen gas:
$n_H = 2 \times n = 2 \times 5.995 \times 10^{-5} \text{ mol} = 1.199 \times 10^{-4} \text{ mol}$
This number of moles of hydrogen represents the number of moles of alcoholic hydrogen atoms in the $1.84$ mg sample of the compound 'X'.
We can determine the number of moles of compound 'X' in the sample by dividing the mass of the sample by the molar mass of the compound:
$n_X = \frac{m}{M}$
where:
- $n_X$ is the number of moles of 'X',
- $m$ is the mass of 'X', and
- $M$ is the molar mass of 'X'.
Substituting in the given values:
$n_X = \frac{1.84 \text{ mg}}{92 \text{ g/mol}} = \frac{1.84 \times 10^{-3} \text{ g}}{92 \text{ g/mol}} = 2.0 \times 10^{-5} \text{ mol}$
The number of alcoholic hydrogens per molecule of 'X' is then given by the ratio of the number of moles of hydrogen to the number of moles of 'X':
$\frac{n_H}{n_X} = \frac{1.199 \times 10^{-4} \text{ mol}}{2.0 \times 10^{-5} \text{ mol}} = 6$
So, compound 'X' contains $6$ alcoholic hydrogens.
2L of 0.2M H2SO4 is reacted with 2L of 0.1M NaOH solution, the molarity of the resulting product Na2SO4 in the solution is _________ millimolar. (Nearest integer)
Explanation:
Molarity of $\mathrm{Na}_2 \mathrm{SO}_4$ is $\frac{0.1}{4}=0.025 \,\mathrm{M}$
$=25 \,\mathrm{mM}$
In the given reaction,
$X+Y+3 Z \leftrightarrows X YZ_{3}$
if one mole of each of $X$ and $Y$ with $0.05 \mathrm{~mol}$ of $Z$ gives compound $X Y Z_{3}$. (Given : Atomic masses of $X, Y$ and $Z$ are 10, 20 and 30 amu, respectively.) The yield of $X YZ_{3}$ is _____________ g. (Nearest integer)
Explanation:
Limiting reagent is $Z=\frac{0.05}{3}=.016$
3 moles of $Z \rightarrow 1$ mole of $X Y Z_{3}$
$0.05$ mole of $Z \rightarrow \frac{1}{3} \times 0.05$ mole of $X Y Z_{3}$
M.wt. of $\mathrm{XYZ}_{3}=10+20+90$
$=120\, \mathrm{amu}$
Wt. of $X Y Z_{3}=\frac{.05}{3} \times 120$
$=2 \mathrm{~g}$
On complete combustion of $0.492 \mathrm{~g}$ of an organic compound containing $\mathrm{C}, \mathrm{H}$ and $\mathrm{O}$, $0.7938 \mathrm{~g}$ of $\mathrm{CO}_{2}$ and $0.4428 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ was produced. The % composition of oxygen in the compound is ___________.
Explanation:
$ \begin{aligned} &=\frac{2}{18} \times \frac{0.4428}{0.492} \times 100 \\\\ &=0.11 \times 0.9 \times 100 \\\\ &=0.099 \times 100=9.9 \end{aligned} $
$\%$ of $C=\frac{12}{44} \times \frac{0.7938}{0.492} \times 100$
$ \begin{aligned} &=0.27 \times 1.61 \times 100 \\\\ &=43.47 \end{aligned} $
$\% \text { Oxygen }=100-(43.47 + 9.9)$
$=100-53.37 \simeq 46$
$20 \mathrm{~mL}$ of $0.02 \,\mathrm{M} \,\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ solution is used for the titration of $10 \mathrm{~mL}$ of $\mathrm{Fe}^{2+}$ solution in the acidic medium.
The molarity of $\mathrm{Fe}^{2+}$ solution is __________ $\times \,10^{-2}\, \mathrm{M}$. (Nearest Integer)
Explanation:
$ \begin{aligned} &10 \times 1 \times M=20 \times 6 \times .02 \\\\ &M=24 \times 10^{-2} M \end{aligned} $
$\therefore $ Answer will be 24
A $100 \mathrm{~mL}$ solution of $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{MgBr}$ on treatment with methanol produces $2.24 \mathrm{~mL}$ of a gas at STP. The weight of gas produced is _____________ mg. [nearest integer]
Explanation:
As $2.24 \,\mathrm{ml}$ is formed at STP.
Number of moles of ethane gas produced
$ =\frac{2.24 X}{22.4} $
$=10^{-4}\, \mathrm{ml}$
Mass of ethane produced $=10^{-4} \times 30=3 \times 10^{-}=3\mathrm{mg}$
Chlorophyll extracted from the crushed green leaves was dissolved in water to make $2 \mathrm{~L}$ solution of Mg of concentration $48\, \mathrm{ppm}$. The number of atoms of $\mathrm{Mg}$ in this solution is $x \times 10^{20}$ atoms. The value of $x$ is ___________. (Nearest Integer)
(Given : Atomic mass of $\mathrm{Mg}$ is $24 \mathrm{~g} \mathrm{~mol}^{-1} ; \mathrm{N}_{\mathrm{A}}=6.02 \times 10^{23} \mathrm{~mol}^{-1}$ )
Explanation:
Number of atoms of $\mathrm{Mg}=\frac{96 \times 10^{-3}}{24} \times \mathrm{N}_{\mathrm{A}}$
$ \begin{aligned} &=4 \times 10^{-3} \times 6 \times 10^{23} \\ &=24 \times 10^{20} \end{aligned} $
$x=24$
When 800 mL of 0.5 M nitric acid is heated in a beaker, its volume is reduced to half and 11.5 g of nitric acid is evaporated. The molarity of the remaining nitric acid solution is x $\times$ 10$-$2 M. (Nearest integer)
(Molar mass of nitric acid is 63 g mol$-$1)
Explanation:
Moles of $\mathrm{HNO}_{3}=400 \times 10^{-3} = 0.4 \text { moles }$
Weight of $\mathrm{HNO}_{3}=0.4 \times 63 \mathrm{~g} =25.2 \mathrm{~g} $
Remaining acid $=25.2-11.5 =13.7 \mathrm{~g} $
$ \begin{aligned} M &=\frac{13.7 \times 1000}{400 \times 63} \\ &=\frac{137}{252}=0.54 \\ &=54 \times 10^{-2} \end{aligned} $
56.0 L of nitrogen gas is mixed with excess hydrogen gas and it is found that 20 L of ammonia gas is produced. The volume of unused nitrogen gas is found to be _________ L.
Explanation:
Since $\mathrm{H}_{2}$ is in excess and $20 \mathrm{~L}$ of ammonia gas is produced.
Hence, 2 moles $\mathrm{NH}_{3} \equiv 1$ mole $\mathrm{N}_{2} \quad(v \propto \mathrm{n})$
$ 20 \mathrm{~L} \mathrm{NH}_{3} \equiv 10 \mathrm{~L} \mathrm{~N}_{2} $
Volume of $\mathrm{N}_{2}$ left $=56-10$
$ =46 \mathrm{~L} $
A sample of 4.5 mg of an unknown monohydric alcohol, R-OH was added to methylmagnesium iodide. A gas is evolved and is collected and its volume measured to be 3.1 mL. The molecular weight of the unknown alcohol is __________ g/mol. [Nearest integer]
Explanation:
moles of alcohol $(\mathrm{ROH}) \equiv$ moles of $\mathrm{CH}_{4}$
At STP, [Assuming STP]
1 mole corresponds to $22.7 \mathrm{~L}$
Hence, $3.1 \mathrm{~mL} \equiv \frac{3.1}{22700} \mathrm{~mol}$
So, moles of alcohol $=\frac{3.1}{22700}$
$\Rightarrow \frac{3.1}{22700}=\frac{4.5 \times 10^{-3}}{\mathrm{M}}$
$M \simeq 33 \mathrm{~g} / \mathrm{mol}$
Blister copper is produced by reaction of copper oxide with copper sulphide.
2Cu2O + Cu2S $\to$ 6Cu + SO2
When 2.86 $\times$ 103 g of Cu2O and 4.77 $\times$ 103 g of Cu2S are used for reaction, the mass of copper produced is _____________ g. (nearest integer)
(Atomic mass of Cu = 63.5 a.m. u, S = 32.0 a.m. u, O = 16.0 a.m. u)
Explanation:
moles of $\mathrm{Cu}_{2} \mathrm{S}=\frac{4.77 \times 10^{3}}{159}=30$
$\mathrm{Cu}_{2} \mathrm{O}$ is limiting reagent
$ \begin{array}{lccc} 2 \mathrm{Cu}_{2} \mathrm{O} & + & \mathrm{Cu}_{2} \mathrm{~S} \longrightarrow & 6 \mathrm{Cu} & + & \mathrm{SO}_{2} \\ 20 && 30 & - & & - \\ - & &20 & 60 & & 10 \end{array} $
Mass of copper $=60 \times 63.5=3810 \mathrm{~g}$
The complete combustion of 0.492 g of an organic compound containing 'C', 'H' and 'O' gives 0.793 g of CO2 and 0.442 g of H2O. The percentage of oxygen composition in the organic compound is ______________. (nearest integer)
Explanation:
Total organic compound = 0.492 gm
Produced CO2 = 0.793 gm
$\therefore$ Moles of CO2 = ${{0.793} \over {44}}$
$\therefore$ Moles of C atoms = ${{0.793} \over {44}}$
$\therefore$ Weight of C atoms = ${{0.793} \over {44}}$ $\times$ 12 = 0.216 g
Produced H2O = 0.442 gm
$\therefore$ Moles of H2O = ${{0.442} \over {18}}$
$\therefore$ Moles of H atoms = ${{0.442} \over {18}}$
$\therefore$ Weight of H atoms = ${{0.442} \over {18}}$ $\times$ 2 = 0.05 g
$\therefore$ Weight of O atoms
= 0.492 $-$ (0.216 + 0.05)
= 0.226 gm
% by mass of oxygen in compound
= ${{0.226} \over {0.492}}$ $\times$ 100 = 46%
116 g of a substance upon dissociation reaction, yields 7.5 g of hydrogen, 60 g of oxygen and 48.5 g of carbon. Given that the atomic masses of H, O and C are 1, 16 and 12, respectively. The data agrees with how many formulae of the following?
A. CH3COOH, B. HCHO, C. CH3OOCH3, D. CH3CHO
Explanation:
Relative atomicities $=\mathrm{H} \Rightarrow 6.5$
$ \begin{aligned} &\mathrm{O} \Rightarrow \frac{51.7}{16}=3.25 \\\\ &\mathrm{C} \Rightarrow \frac{41.8}{12}=3.5 \end{aligned} $
Emperically formula is approx.. $\mathrm{CH}_2 \mathrm{O}$
(A) $\mathrm{C}_2 \mathrm{H}_4 \mathrm{O}_2$ (B) $\mathrm{CH}_2 \mathrm{O}$ relate to this formula.
Two elements A and B which form 0.15 moles of A2B and AB3 type compounds. If both A2B and AB3 weigh equally, then the atomic weight of A is _____________ times of atomic weight of B.
Explanation:
Let atomic weight of A = x
and atomic weight of B = y
$\therefore$ Molar mass of A2B = 2x + y
and molar mass of AB3 = x + 3y
Now, weight of 0.15 moles of A2B = (2x + y) 0.15
and weight of 0.15 moles of AB3 = (x + 3y) 0.15
Given, weight of 0.15 moles of A2B and AB3 are equal.
$\therefore$ (2x + y)0.15 = (x + 3y)0.15
$\Rightarrow$ x = 2y
$ \Rightarrow {x \over y} = 2$
$\therefore$ Atomic weight of A is 2 times of atomic weight of B.
CNG is an important transportation fuel. When 100 g CNG is mixed with 208 g oxygen in vehicles, it leads to the formation of CO2 and H2O and produces large quantity of heat during this combustion, then the amount of carbon dioxide, produced in grams is ____________. [nearest integer]
[Assume CNG to be methane]
Explanation:
Initially,
Mass of CNG(CH4) = 100 gm
$\therefore$ Moles of CH4 = ${{100} \over {16}}$ = 6.25 moles
Mass of O2 = 208 gm
$\therefore$ Moles of O2 = ${{208} \over {32}}$ = 6.5 moles
From reaction you can see,
1 mole of CH4 react with 2 mole of O2
$\therefore$ 6.25 mole of CH4 react with 6.25 $\times$ 2 = 12.5 moles of O2
But here only 6.5 moles of O2 present
So, O2 will act as limiting reagent.
$\therefore$ Produced CO2 will depends on moles of O2.
From 2 moles of O2 1 mole of CO2
$\therefore$ From 6.5 moles of O2 ${{6.5} \over {2}}$ moles of CO2 produced.
$\therefore$ Weight of CO2 = ${{6.5} \over {2}}$ $\times$ 44 = 143 gm
The moles of methane required to produce 81 g of water after complete combustion is _____________ $\times$ 10$-$2 mol. [nearest integer]
Explanation:
POAC on $\mathrm{H}$ atom
$ \begin{aligned} &\mathrm{n}_{\mathrm{CH} 4} \times 4=\mathrm{n}_{\mathrm{H} 2 \mathrm{O}} \times 2 \\\\ &\mathrm{n}_{\mathrm{CH}_4}=\frac{81}{18} \times 2 \times \frac{1}{4}=\frac{81}{36} \\\\ &\mathrm{n}_{\mathrm{CH}_4}=2.25 \\\\ &=225 \times 10^{-2} \end{aligned} $
Nearest Integers $=225$
On complete combustion 0.30 g of an organic compound gave 0.20 g of carbon dioxide and 0.10 g of water. The percentage of carbon in the given organic compound is _____________. (Nearest integer)
Explanation:
${C_x}{H_y} + \left( {x + {y \over 4}} \right){O_2} \to x\,C{O_2} + {y \over 2}{H_2}O$
Given organic compound CxHy= 0.3 gm
Produced carbon dioxide (CO2) = 0.2 gm
Produced water (H2O) = 0.1 gm
Moles of CO2 = ${{0.2} \over {44}}$
$\therefore$ Moles of C atom = ${{0.2} \over {44}}$
$\therefore$ Mass of C atom = ${{0.2} \over {44}}$ $\times$ 12 = 0.0545
Moles of H2O = ${{0.1} \over {18}}$
$\therefore$ Moles of H atoms = ${{0.1} \over {18}}$ $\times$ 2
$\therefore$ Mass of H atoms = ${{0.1} \times2\over {18}}$ $\times$ 1 = 0.0111
$\therefore$ % of C atom = ${{0.0545} \over {0.3}}$ $\times$ 100 = 18%
A protein 'A' contains 0.30% of glycine (molecular weight 75). The minimum molar mass of the protein 'A' is __________ $\times$ 103 g mol$-$1 [nearest integer]
Explanation:
Let, molar mass of protein A = x
Protein A contains 0.30% glycine
$\therefore$ ${{x \times 0.3} \over {100}} = 75$
$\Rightarrow$ x = 25000 = 25 $\times$ 103
The number of N atoms in 681 g of C7H5N3O6 is x $\times$ 1021. The value of x is (NA = 6.02 $\times$ 1023 mol$-$1) (Nearest Integer)
Explanation:
First, determine the molar mass of the compound C$_7$H$_5$N$_3$O$_6$:
Carbon (C): 12 g/mol, and there are 7 C atoms: $7 \times 12 = 84 \text{ g/mol}$
Hydrogen (H): 1 g/mol, and there are 5 H atoms: $5 \times 1 = 5 \text{ g/mol}$
Nitrogen (N): 14 g/mol, and there are 3 N atoms: $3 \times 14 = 42 \text{ g/mol}$
Oxygen (O): 16 g/mol, and there are 6 O atoms: $6 \times 16 = 96 \text{ g/mol}$
Calculate the total molar mass:
$ \text{Molar mass of C}_7\text{H}_5\text{N}_3\text{O}_6 = 84 + 5 + 42 + 96 = 227 \text{ g/mol} $
Calculate the number of moles of C$_7$H$_5$N$_3$O$_6$ in 681 grams:
$ \text{Moles of C}_7\text{H}_5\text{N}_3\text{O}_6 = \frac{681 \text{ g}}{227 \text{ g/mol}} = 3 \text{ moles} $
Each molecule of C$_7$H$_5$N$_3$O$_6$ contains 3 nitrogen atoms. Thus, in 3 moles, the total moles of nitrogen atoms is:
$ \text{Moles of N atoms} = 3 \times 3 = 9 \text{ moles} $
Using Avogadro's number, calculate the number of nitrogen atoms:
$ \text{Number of N atoms} = 9 \text{ moles} \times 6.02 \times 10^{23} \text{ atoms/mole} $
$ = 54.18 \times 10^{23} = 5.418 \times 10^{24} \text{ N atoms} $
Convert this number to the form $ x \times 10^{21} $:
$ 5.418 \times 10^{24} = 5418 \times 10^{21} $
Thus, the value of $ x $ is:
$ x = 5418 $
1 L aqueous solution of H2SO4 contains 0.02 m mol H2SO4. 50% of this solution is diluted with deionized water to give 1 L solution (A). In solution (A), 0.01 m mol of H2SO4 are added. Total m mols of H2SO4 in the final solution is ___________ $\times$ 103 m mols.
Explanation:
$=0.01 \mathrm{~m} \mathrm{~mol}$.
$\mathrm{n}_{\mathrm{H}_2 \mathrm{SO}_4}$ in Final solution $=0.01+0.01$
$=0.02 \,\mathrm{m\,mol}$
$=0.00002 \times 10^3 \mathrm{m\,mol}$
The answer 0
Number of grams of bromine that will completely react with 5.0 g of pent-1-ene is ___________ $\times$ 10$-$2 g. (Atomic mass of Br = 80 g/mol) [Nearest Integer]
Explanation:
Molar mass of C5H10 = 12 $\times$ 5 + 10 = 70 gm
Given mass of C5H10 = 5 gm
$\therefore$ Moles of C5H10 = ${5 \over {70}}$
From reaction,
1 mole of C5H10 reacts with 1 mole of Br2
$\therefore$ ${5 \over {70}}$ moles of C5H10 reacts with ${5 \over {70}}$ moles of Br2
$\therefore$ Reacted Br2 = ${5 \over {70}}$ $\times$ 160 gm
= 11.428 gm
= 1142.8 $\times$ 10$-$2 gm
$\simeq$ 1143 $\times$ 10$-$2 gm
A 0.166 g sample of an organic compound was digested with conc. H2SO4 and then distilled with NaOH. The ammonia gas evolved was passed through 50.0 mL of 0.5 N H2SO4. The used acid required 30.0 mL of 0.25 N NaOH for complete neutralization. The mass percentage of nitrogen in the organic compound is ____________.
Explanation:
Millimoles of $\mathrm{NH}_{3}=30 \times 0.25=7.5$
Mass $\%$ of nitrogen $=\frac{7.5}{0.166} \times 10^{-3} \times 14 \times 100 \simeq 63 \%$
[Given : NA = 6.02 $\times$ 1023 mol$-$1
Atomic mass of Na = 23.0 u]
Explanation:
Molar mass of Na = 23 gmol$-$1
${{Weight\,of\,sodium\,atom} \over {Molecular\,mass\,of\,sodium\,atom}} = {{Number\,of\,atoms} \over {Avogadro's\,number}}$
${{8g} \over {23g}} = {{Number\,of\,atoms} \over {6.022 \times {{10}^{23}}}}$
Number of atoms $ = {{8 \times 6.022} \over {23}} \times {10^{23}}$
Number of atoms = 2.09 $\times$ 1023
x $\approx$ 2
Hence, answer is 2.
[Atomic masses Cu : 63.54u, S : 32u, O : 16u, H : 1u]
Explanation:
The concentration of copper sulphate solution is x $\times$ 10$-$3 mol/L.
Molarity = ${{Number\,of\,moles\,of\,solute} \over {Volume\,of\,solution(L)}}$ ..... (i)
Molar mass of CuSO4 . 5H2O = 63.54 + 32 + 16 $\times$ 4
= 5 $\times$ 18 = 249.54 g/mol
Number of moles of solute = ${{Weight\,of\,solute} \over {Molecular\,mass\,of\,solute}}$
= ${{80g} \over {249.54g/mol}}$ = 0.32 mol
Volume of solution = 5 L
From Eq. (i),
Molarity = ${{0.3205} \over 5}$ = 64.11 $\times$ 10$-$3 mol/L
$\therefore$ x = 64.11
or x $\approx$ 64
Hence, answer is 64.
Explanation:
${{20} \over {62}}$ moles
Moles of NaOH formed = ${{20} \over {62}}$ $\times$ 2
[NaOH] = ${{{{40} \over {62}}} \over {{{500} \over {1000}}}}$ = 1.29 M = 13 $\times$ 10$-$1 M (Nearest integer)