Tag: chemistry

Questions Related to chemistry

The number of electrons which will together weigh one gram is :

introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

  1. $1.098 \times 10^{27}$ electrons

  2. $9.1096\times 10^{31}$ electrons

  3. 1 electrons

  4. $1\times 10^4$ electrons

Show answer
Correct Option: A
Explanation:

Mass of a electrons = $9.1096\times 10^{-31}Kg$
1g or $10^{-3}kg = \dfrac{1}{9.1096\times 10^{-31}}\times 10^{-3}$
=$1.098\times 10^{27}$ electons

What is the mass of oxalic acid, $ H _{2}C _{2}O _{4},$ which can be oxidized to $ CO _{2}$ by 100 ml of $MnO _{4}^{-}$ solution, 10 ml of which is capable of oxidizing 50 ml of $ 1.00 N\ I^{-} $ to $ I _{2}?$

introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

  1. 2.25 g

  2. 52.2 g

  3. 25.2 g

  4. 22.5 g

Show answer
Correct Option: D
Explanation:

Balanced chemical reaction,
$2KMnO _{4}+5H _{2}C _{2}O _{4}+3H _{2}SO _{4}\rightarrow 2MnSO _{4}+10CO _{2}+K _{2}SO _{4}+8H _{2}O$

$(KMnO _{4})N _{1}V _{1}= N _{2}V _{2}(I _{2})$

$N _{1}\times 10= 1\times 50$

$N _{1}= 5N$

n-factor for $KMnO _{4}= 7-2=5$

Moles of $KMnO _{4}=\dfrac{5}{5}=1$

2 mole $KMnO _{4}= 5$ mole $H _{2}C _{2}O _{4}$

1 mole $KMnO _{4}= 2.5$ mole $H _{2}C _{2}O _{4}$

In 100 mL or 0.1 L $= 0.1\times 2.5= 0.25$ moles
Mass of $H _{2}C _{2}O _{4}= 0.25\times 90= 22.5g$

A definite mass of $ H _{2}O _{2} $ is oxidized by excess of acidified $ KMnO _{4} $ and acidified $ K _{2}Cr _{2}O _{7} $, in separate experiments. Which of the following is/are correct statements? 
(K = 39, Cr = 52, Mn = 55 )

introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

  1. Mass of $ K _{2}Cr _{2}O _{7} $ used up will be greater than that of $ KMnO _{4} $

  2. Moles of $ KMnO _{4} $ used up will be greater than that of $ K _{2}Cr _{2}O _{7} $

  3. Equal mass of oxygen gas is evolved in both the experiments.

  4. If equal volumes of both the solutions are used for complete reaction, then the molarities of $ KMnO _{4} $ and $ K _{2}Cr _{2}O _{7} $ solutions are in $6:5$ ratio.

Show answer
Correct Option: A,B,D
Explanation:

According to question, reaction of experiment (1) and (2)
(1)$ 5H _{2}O _2+2KMnO _{4}+3H _{2}SO _{4}\rightarrow 5O _{2}+2MnSO _{4}+K _{2}SO _{4}+8H _{2}O $


(2)$ 3H _{2}O _{2}+K _{2}Cr _{2}O _{7}+4H _2SO _{4}\rightarrow Cr _{2}(SO _{4}) _{3}+3O _{2}+K _{2}SO _{4}+7H _{2}O $

(a) According to reaction (1)
5 mole $ H _{2}O _{2} = 2\,mole KMnO _{4} $

1 mole $ H _{2}O _{2} = \dfrac{2}{5} = 0.4\,mole\,KMnO _{4} = 63.2\,g\,KMnO _{4} $

According to reaction (2)
3 mole $ H _{2}O _{2} = 1\,mole\,K _{2}Cr _{2}O _{7} $

1 mole $ H _{2}O _{2} = \dfrac{1}{3} mole\,K _{2}Cr _{2}O _{7} = 98.1 g \, K _{2}Cr _{2}O _{7} $

Mass of $ K _{2}Cr _{2}O _{7}> KMnO _{4} $

(b) Moles of $ KMnO _{4}> $ moles of $ K _{2}Cr _{2}O _{7} (0.333) $

(c)In reaction 1, 5 Mole $ H _{2}O _{2} $ released = 5 mole $ O _{2}\Rightarrow 32\times 5=160g $
In reaction 2, 3 mole $ H _{2}O _{2} $ released = 3 mole $ O _{2}=3\times 32= 96 g$ 

(d) 1 mole of $ H _{2}O _{2} = \dfrac{2}{5} $ moles $ KMnO _{4} $ exp...(1)
1 mole of $ H _{2}O _{2} = \dfrac{1}{3}$ mole $ K _{2}Cr _{2}O _{7} $ exp...(2)
$ \dfrac{KMnO _{4}}{K _{2}Cr _{2}O _{7}} = \dfrac{\dfrac{2}{5}}{\dfrac{1}{3}} = \dfrac{2}{5}\times \dfrac{3}{1} = \dfrac{6}{5}\Rightarrow 6:5 $

Options A, B and D are correct.

Two acids $ H _{2}SO _{4} $ and $ H _{3}PO _{4} $ are neutralized separately by the same amount of an alkali when sulphate and dihydrogen orthophosphate are formed, respectively. Find the ratio of the masses of $ H _{2}SO _{4} $ and $ H _{3}PO _{4} $ 

introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

  1. $ 1:1 $

  2. $ 1:2 $

  3. $ 2:1 $

  4. $ 2:3 $

Show answer
Correct Option: B
Explanation:

$H _{2}SO _{4}+2NaOH\rightarrow Na _{2}SO _{4}+2H _{2}O$

$H _{3}PO _{4}+NaOH\rightarrow NaH _{2}PO _{4}+H _{2}O$

Equivalent of alkali $= 19$ eq of $H _{2}SO _{4}= 1g$ eq of $H _{3}PO _{4}$

Two acids must be reacting in the ratio of their equivalent masses

Eq. wt. of $H _{2}SO _{4}=\dfrac{98}{2}=49$

Eq. wt. of $H _{3}PO _{4}= \dfrac{98}{1}=98$

$\therefore $ ratio of masses of $H _{2}SO _{4}$ & $H _{3}PO _{4}$
$49:98=1:2$

$\Rightarrow 1:2$

A gaseous alkane is exploded with oxygen. The volume of ${O} _{2}$ for complete combustion of alkane to $C{O} _{2}$ formed is in the ratio $7:4$. The molecular formula of alkane is:

introduction to mole gas laws and mole concept atoms and molecules chemistry mole concept chemical formula and mole concept

  1. ${C} _{2}{H} _{6}$

  2. ${C} _{3}{H} _{8}$

  3. ${C} _{4}{H} _{10}$

  4. $C{H} _{4}$

Show answer
Correct Option: A
Explanation:

The balanced reaction is given below:


${C} _{n}{H} _{2n+2} +[n+\displaystyle\frac{n+1}{2}]{O} _{2}\rightarrow nC{O} _{2} +(n+1){H} _{2}O$

Given, 

$\displaystyle\dfrac{n+\dfrac{n+1}{2}}{n}=\dfrac{7}{4}\implies n=2$

Hence, the alkane is ${C} _{2}{H} _{6}$.

Hence, the correct option is $A$

Formation of nylons and polyesters are called step growth polymerization because:

types of polymerisation reactions condensation polymerisation polymer polymers chemistry

  1. the polymers are formed by adding a monomer step by step

  2. the polymers are formed by condensation and monomers are joined by loss of simple molecules like water

  3. the monomers used for condensation are unsaturated molecules

  4. the polymers are formed by addition of a large number of free radicals formed by monomers

Show answer
Correct Option: B
Explanation:
 These polycondensation reactions result in the loss of some simple molecules as water, alcohol, etc., and lead to the formation of high molecular mass condensation polymers.
let's look at the formation of nylon polymer
Nylon 6,6- It is prepared by the condensation polymerisation of hexamethylenediamine with adipic acid under high pressure and at high temperature with the removal of water molecules.
the correct option is [B].

Terylene is a condensation polymer of ethylene glycol and:

types of polymerisation reactions condensation polymerisation polymer polymers chemistry

  1. benzoic acid

  2. phthalic acid

  3. terephthalic acid

  4. salicylic acid

Show answer
Correct Option: C
Explanation:

Terylene is a condensation polymer of ethylene glycol and terephthalic acid,

it is the product of condensation polymerisation, this type of polymerisation generally involves a repetitive condensation reaction between two bi-functional monomers and lead to the formation of high molecular mass condensation polymers.
The correct option is [C].

Which of the following is not true about polymers?

types of polymerisation reactions condensation polymerisation polymer polymers chemistry

  1. Polymers are high molecular mass macro-molecules.

  2. Polymers may be of natural or synthetic origin.

  3. Condensation polymers are made up of one type of monomers only.

  4. They have high viscosity and do not carry any charge.

Show answer
Correct Option: C
Explanation:

A) Polymers are high molecular mass macro-molecules made with a large number of repeating subunits.

B) Naturally occurring polymers - Silk, Wool, DNA, etc.
Synthetic polymers- Nylon, Polyethylene, Polyester etc. 
C) Two bi-functional monomers are used in condensation polymerisation,
Example Nylon-6,6 is the polymer of Hexamethylenediamine + adipic acid

So this statement is false.

D) Polymers are large chain molecules so they have high viscosity. Since monomers of polymers are neutral, the overall polymer is also neutral.

$X-(CH _2) _4-X \xrightarrow [{HOOC-(CH _2) _4-COOH}] {Y}:Condensation : Polymer$


The correct functional group $X$ and the reagent/reaction conditions $Y$ in the following scheme are:

types of polymerisation reactions condensation polymerisation polymer polymers chemistry

  1. $X=COOCH _{3},\ Y=H _{2}/Ni/heat$

  2. $X=CONH _{2},\ Y=H _{2}/Ni/heat$

  3. $X=CONH _{2},\ Y=Br _{2}/NaOH$

  4. $X=CN,\ Y=H _{2}/Ni/heat$

Show answer
Correct Option: C,D

 Which of the following is condensation polymer? 

types of polymerisation reactions condensation polymerisation polymer polymers chemistry

  1. Polypropylene

  2. PMMA

  3. Glyptal

  4. Teflon

Show answer
Correct Option: A