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97401.

The position of fical image formed by the given lens combination from the third lens will be at a distance of `f_1=+10cm,f_2=-10cm,f_3=+30`A. 15 cmB. infinityC. 45 cmD. 30 cm

Answer» Correct Answer - 4
For 1 st lens, `u_(1)=-30,f_(1)=+10,`
Formal of lens `=(1)/(v_(1))-(1)/(u_(1))=(1)/(f_(1))`
`therefore(1)/((v_(1)))+(1)/(10)=(1)/(10)`
or `v_(1)=1` om at `I_(1)` behind the lens. The imgage `I_(1)` serves as virtual object for concave lens. For second lens, which is concave,
`u_(2)=(15-5)=10cm.`
Image distance from third lens `f_(3)=30 cm.`
97402.

Correct order of basic strength in gas phase is (I) `CH_(3)-NH_(2)` (II) `(CH_(3))_(2)NH` (III) `(CH_(3))_(3)N` (IV) `NH_(3)`A. `A gt B gt C`B. `B gt A gt C`C. `A gt C gt B`D. `C gt A gt B`

Answer» Correct Answer - B
97403.

The Gayatri Mantra contained in the Rigveda is dedicated to which deity?1. Savitri2. Agni3. Marut4. Indra

Answer» Correct Answer - Option 1 : Savitri

The correct answer is Savitri.

  • Gayatri has been revered as Savitur (Sun God).
  • Savitur is also called Savitri.
  • The popular 'Gayatri Mantra' is given in the third mandala of the Rig Veda, which is dedicated to the god Savitur (Savitri).
  • Gayatri Mantra has been composed by Maharishi Vishwamitra.

  • The Rigveda is an ancient Indian collection of Vedic Sanskrit hymns.
  • It is one of the four sacred canonical texts (śruti) of Hinduism known as the Vedas.
  • The Rigveda is the oldest known Vedic Sanskrit text. 
97404.

In a `S_(N^(2))` substitution reaction of the type `R-Br+Cl^(-)overset("DMF")rarrR-Cl+Br^(-)` Which one of the following has the highest relative rate?A. `(CH_(3))_(3)C-CH_(2)Br`B. `CH_(3)CH_(2)Br`C. `CH_(3)CH_(2)CH_(2)Br`D. `(CH_(3))_(2)CH-CH_(2)Br`

Answer» Correct Answer - B
97405.

In CH4, NH3 and H2O, the central atom undergoes sp3 hybridisation-yet their bond angles are different, why?

Answer»

1. In CH4, NH3 and H2O the central atom undergoes sp3 hybridisation. But their bond angles are different due to .the presence of lone pair of electrons. 

2. It can be explained by VSEPR theory. According to this theory, even though the hybridisation is same, the repulsive force between the bond pairs and lone pairs are not same. 

3. Bond pair – Bond pair < Bond pair – Lone pair < Lone pair -Lone pair So due to the varying repulsive force the bond pairs and lone pairs are distorted from regular geometry and organise themselves in such a way that repulsion will be minimum and stability will be maximum. 

4. In case of CH4 , there are 4 bond pairs and no lone pair of electrons. So it remains in its regular geometry, i.e., tetrahedral with bond angle = 109° 28.'

5. H2O has 2 bond pairs and 2 lone pairs. There is large repulsion between lp – lp. Again repulsion between lp – bp is more than that of 2 bond pairs. So 2 bonds are more restricted to form inverted V shape (eg;) bent shape molecule with a bond angle of 104° 35. 

6. NH3 has 3 bond pairs and 1 lone pair. There is repulsion between lp – bp. So 3 bonds are. more restricted to form pyramidal shape with bond angle equal to 107° 18’.

97406.

Bond order is a term commonly used in MO theory. 1. How is it calculated? 2. How is it related to bond length and bond energy?

Answer»

1. Bond order = ½ (Nb -Na

where Nb = No. of electrons occupying bonding orbitals and Na = No. of electrons occupying antibonding orbitals.

2. As the bond order increases, bond length decreases and bond energy increases, i.e., bond order is directly proportional to bond energy and inversely proportional to bond length.

97407.

Write the type of hybridisation of each carbon in the compound. CH3 -CH=CH-CN

Answer»

Carbon 1 → sp³ 

Carbon 2 → sp² 

Carbon 3 → sp² 

Carbon 4 → sp

97408.

Read the following lines and answer the questions that follow.Some are like fields of sunlit corn, Meet for a bride on her bridal morn, Some, like the flame of her marriage fire, Or, rich with the hue of her heart’s desire, Tinkling, luminous, tender, and clear, Like her bridal laughter and bridal tear. (i) What are the bangles made for a bride’s bridal morn compared to?(ii) Which flame are some bangles like?(iii) What adjectives are used to describe the bangles?(iv) What is like a bride’s laughter and tear?

Answer»

(i) They are compared to fields of sunlit corn.

(ii) Some bangles are like the flame of a marriage fire.

(iii) Tinkling, luminous, tender, and clear.

(iv) Bangles.

97409.

Write an application to the Deputy Superintendent of Police to allow you to use loudspeaker on the occasion of marriage of your sister.

Answer»

To
The Deputy Superintendent of Police,
Bareilly.
Dated : March 18th, 20….

Sir,

Şubject : Request for use of Loudspeaker Permit. Most respectfully, I beg to say that the marriage ceremony of my younger sister Beena will be performed on Nov. 24th, 20… So I need to use loudspeaker for the function. I, therefore, request you to grant permission for use of loudspeaker from 4 P.M. to 10 P.M. on Nov. 24th, 20….I shall be highly obliged…..

Yours faithfully,
Satya Prakash Gupta
(Address………………)

97410.

In the formation of methane, carbon undergoes sp3 hybridisation. 1. What do you mean by sp3 hybridisation? 2. Give the % s-character and pcharacter of an sp3 hybrid orbital. 3. What is the bond angle in methane? 4. What is the geometry of methane molecule?

Answer»

1. sp3 hybridisation involves mixing up of one – s and three-p orbitals of the valence shell of an atom to form four sp3 hybrid orbitals of equivalent energies and shape. 

2. Each sp3 hybrid orbital has 25% scharacter and 75% p-character. 

3. The angle between the sp3 hybrid orbitals in methane is 109°28′. 

4. Tetrahedron.

97411.

The phenomenon of ‘like begets like’ is due to

Answer»

The answer is 'heredity'

The phenomenon of genetic transfer of characteristics from one generation to the next, where an offspring  expresses characteristics similar to that of the parent is like begets like. This phenomenon is best understood when the offspring of a mango plant is a mango plant and that of a human is a human and not a monkey or a lion.

97412.

Mycoglobin is a

Answer»

Myoglobin is a protein located primarily in the striated muscles of vertebrates. MB is the gene encoding myoglobin in humans. It encodes a single polypeptide chain with one oxygen binding site. Myoglobin contains a heme prosthetic group that can reversibly bind to oxygen.

97413.

Blackened oil painting can be restored into original form by the action ofA. ChlorineB. `BaO_(2)`C. `H_(2)o_(2)`D. `Mno_(2)`

Answer» Correct Answer - C
`{:(PbO+ h_(2)S to Pbs+ H_(2)O),(("white")" "("air")" "("Bloack")),(Pbs+ 4H_(2)O_(2) to PbSO_(4) + 4H_(2)O),("black "" "("white")):}`
97414.

(I) Arrange NH3, H2O and HF in the order of increasing magnitude of hydrogen bonding and explain the basis for your arrangement? (II) Can we use concentrated sulphuric acid and pure zinc in the preparation of dihydrogen?

Answer»

1. Increasing magnitude of hydrogen bonding among NH3, H2O and HF is 

HF > H2O > NH3 

2. The extent of hydrogen bonding depends upon electronegativity and the number of hydrogne atoms available for bonding. 

3. Among N, F and O the increasing order of their electronegativities are

N < O < F 

4. Hence the expected order of the extent of hydrogen bonding is 

HF > H2O > NH3

(II) Conc. H2SO4 cannot be used because it acts as an oxidizing agent also and gets reduced to SO2

Zn + 2H2SO4 (Conc) → ZnSO4 + 2H2O + SO2 Pure Zn is not used because it is non-porous and reaction will be slow. The impurities in Zn help in constitute of electrochemical couple and speed up reaction.

97415.

Among NH3, H2O and HF, which would you except to have highest magnitude of hydrogen bonding and why?

Answer»

HF, because Fluorine is more electronegative.

97416.

Among NH3 , H2O and HF which would you expect to have highest magnitude of hydrogen bonding? Why?

Answer»

Strength of H-bond depends upon the atomic size and electronegativity of the other atom to which H- atom is covalently bonded. Smaller size and higher electronegativity favour H-bonding. Among N, F and O atoms, F is the smallest and its electronegativity is highest. Hence, HF will have highest magnitude of H-bonding.

97417.

How many of the following compounds have polymeric structure? Boron Nitride, Boric acid, Borazole, Borax, Berylium hydride, Gypsum, Graphite.

Answer» Correct Answer - 4
Boron Nitride, Boric acid, Beryllium hydride, Graphite.
97418.

Thermodynamically most stable allotrope of carbon is ........

Answer»

Thermodynamically most stable allotrope of carbon is Graphite.

97419.

Assertion: Buckministerfullerence is the purest isomeric form of carbon. Graphite is thermodynamically most stable allotrope of carbon.A. DiamondB. GraphiteC. FullereneD. Coal

Answer» Thermodynamically, graphite is the most stable form of carbon.
97420.

Rice, wheat ant potatoes are good source of carbohydrates. This gives energy to our body. Sometimes it burst to form a Gel. To gelatinize the starch present in food items, what will you do? a. You will apply dry-heat on it. b. You will apply moist-heat on it. c. After applying dry heat, you will add moisture to it. d. Both a and c

Answer»

Correct answer is b. You will apply moist-heat on it. 

97421.

For the oxidation of Iron : 4Fe(s) + 3O2(g) → 2Fe2O3(g) Entropy change and Enthalpy change at 298 K are – 549.4 J/K/mol and -1648 × 103 J/mol respectively. Calculate the free energy change for the reaction. Is the reaction spontaneous at 298 K.

Answer»

ΔG = ΔH – TΔS 

ΔG = -1648000 + 163721.2 

= -1484278.8 J/mol 

= -1484.2788 kJ/mol 

The reaction is spontaneous.

97422.

The longest wavelength of light that can be used for the ionisation of lithium atom (Li) in its ground state is x × 10-8 m. The value of x is (Nearest Integer)(Given: Energy of the electron in the first shell of the hydrogen atom is -2.2 × 10-18 J; h=6.63 × 10-34 Js and c = 3 x 108 ms-1)

Answer»

Correct answer is 4

We can not calculate I.E. of lithium atom.

97423.

If 0.02 moles of H2SO4 are present in 1 lit. of solution from which 50% solutions taken out and again diluted upto 1 lit. by adding water and further 0.01 moles of H2SO4 are added than total milimole of H2SO4 in resulting solution is ____.

Answer»

Initial moles of H2SO4 (in/Lit.) = 0.02

In 50% solution moles of H2SO4 = 0.01

Added moles of H2SO4 = 0.01

Total moles of H2SO4 in resulting solution = 0.02 

= 20 x 10-3 moles

= 20 milimoles

97424.

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 × 103 m mols.

Answer»

\(n_{H_2SO_4}\) in Soln A = 50% of original solution

 = 0.01 m mol

\(n_{H_2SO_4}\) in Final solution = 0.01 + 0.01

 = 0.02 mmol

 = 0.00002 x 103 mmol

The answer is 0

97425.

The Vaccine used for whooping cough in children is –(a) B.C.G (b) D.P.T(c) Polio (d) None of these

Answer»

The Vaccine used for whooping cough in children is D.P.T. 

97426.

The decomposition of hydrocarbon follows the equation `k=(4.5xx10^(11)s^(-1))e^(-28000K//T)` Calculate `E_(a)`.

Answer» Correct Answer - `232.79kJ mol^(-10`
According to Arrhenius equation `k=Ae^(-Ea//RT)`
`:. (-E_(a))/(RT)=-(28000K)/(T)`
or `E_(a)=28000KxxR`
`=28000Kxx8.314K ^(-1) mol^(-1)=232.79 kJ mol^(-1)`
97427.

The composition of a hydrocarbon follows the equation K = (4.5 x1011 sec-1) e-28000K/T. Calculate the value of Ea.

Answer»

232.79 kJ/mol

97428.

Find energy of each of the photons which a. correspond to light of frequency `3xx10^(15) Hz`. b. have wavelength of `0.50 Å`.

Answer» i. `E=hv=6.6xx10^(-34)xx3xx10^(15)=1.98xx10^(-18)J`
ii. `E=hc/lambda=(6.6xx10^(-34)J sxx3xx10^(8) m s^(-1))/(0.50xx10^(-10)m)`
`=3.98xx10^(-15) J`
97429.

For a first order reaction time taken for half of the reaction to complete is t1and ¾ of the reaction to complete is t2. How are t1 and t2 related ?

Answer»

t2 = 2t1 because for 3/4th of the reaction to complete time required is equal to two
half lives.

97430.

Esters are functional isomers of :A. Carboxylic acidB. KetonesC. DiketonesD. Diols

Answer» Correct Answer - A
Esters are functional i…………..
Esters are functional isomers of Carboxylic acid.
97431.

For the decomposition of `HI` the following logarithmic plot is shown `: [R=1.98 cal// mol - K]` The activation energy of the reaction is aboutA. `45600 cal`B. `13500 cal`C. `24600 cal`D. `32300 cal`

Answer» Correct Answer - 1
`logk=-(E_(a))/(2.303R)(1)/(T)+"constant"=-(E_(a))/(2.303R)xx10^(-3)xx(10^(3))/(T)+"constant"`
Thus slope of graph will be `-(E_(a)xx10^(-3))/(2.303R)= -(4)/(0.4)`
`implies" "E_(a)=2.303xx1.98xx10^(4)=45600cal`
97432.

Assertion: Order of reaction can never be fractional for an elementary reaction. Reason: An elementary reaction takes place by one step mechanism.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is the correct explanation of the assertion.C. If assertion is true but reason is falseD. If assertion is false but reason is true

Answer» Correct Answer - a
An elemenary is one stag reaction and in such reaction and unodecularty are same .Note that molescularity can never be fractional.
97433.

Ease of esterification of following acids with `CH_(3)OH` is`:` `{:(HCOOH",",CH_(3)COOH",",CH_(3)-CH_(2)-COOH",",CH_(3)-underset(CH_(3))underset(|)(CH)-COOH,),(I,II,III," "III,):}`A. `I=II=III=IV`B. `I gt II gt III gt IV`C. `I lt II lt III lt IV`D. `I gt IV gt III gt II`

Answer» Correct Answer - 2
Rate of esterification `prop (1)/("Steric crowding")`
97434.

The molality of a urea solution in which ` 0.0100 g ` of urea, ` [(NH_(2))_(2)CO] ` is added to ` 0.3000 dm^(3) `of water at STP isA. ` 0. 555 m`B. ` 5.55 xx 10^(-4) m`C. ` 33.3 m`D. ` 3.33 xx 10^(-2) m`

Answer» Correct Answer - B
Molality `=("moles of solute")/("kg of water")`
Moles of unrea` =(0.010)/(60) mol`
Water at `STP (d=1 g/cm^(3) =1 kg//dm^(3)) =0.3 dm^(3) =0.3 kg`
` :.` Molality `=(0010)/(60xx0.3) =5.555 xx10^(-4) m`.
97435.

Consider the acidity of the carboxylic acids: (1) `PhCOOH` (2) `o-NO_(2) C_(6) H_(4) COOH` (3) `p-NO_(2) C_(6) H_(4) COOH` (4) `m-NO_(2) C_(6) H_(4) COOH` Which of the following order is correct?A. ` 2gt 3gt 4gt 1`B. ` 2gt 4gt 3gt 1`C. ` 2gt 4gt 1gt 3`D. ` 1gt 2 gt 3gt 4`

Answer» Correct Answer - A
This is corect order for acidic nature (ortho effect).
97436.

A broadband provider marks up the cost price of an internet plan by 50% and offers a discount of 20%. He asks the customer to pay GST of 18% on the selling price. The customer refuses to pay the tax due to which the provider himself pays the GST. Find his profit or loss percentage.1. \(2\frac{3}{5}\%\) Loss2. \(1\frac{3}{5}\%\) Profit3. \(2\frac{3}{5}\%\) Profit4. No profit no loss5. \(1\frac{3}{5}\%\) Loss

Answer» Correct Answer - Option 5 : \(1\frac{3}{5}\%\) Loss

Given:

Provider marks up 50% above the CP

Discount % = 20%

GST = 18%

Concept used:

Loss = CP – SP

Loss% = {(CP – SP)/CP} × 100

CP = cost price

SP = selling price

MP = marked price

Calculation:

Let CP of internet plan be 2x

MP = 2x × 150% = 3x

SP = 3x × 80% = 12x/5

According to the question,

The provider has paid GST of 18% on SP

So,

Actual amount got by the provider = 12x/5 × 82/100

⇒ 492x/250

Loss = {2x – (492x/250)}

⇒ (500x – 492x)/250

⇒ 8x/250

Loss percentage = {(8x/250)/2x} × 100

⇒ (8x/500x) × 100

⇒ 8/5

⇒ \(1\frac{3}{5}\%\)

∴ Required loss percentage is \(1\frac{3}{5}\%\)

97437.

A shop owner generally gives 30% discount on all products. But during Diwali he decided to bump up the marked price 20% over the previous marked price and gave a discount of 40%. What is the percentage change in his selling price during Diwali?1. 2.862. 2.963. 3.164. 4.965. None of these

Answer» Correct Answer - Option 1 : 2.86

GIVEN :

The shop owner gave 40% discount instead of 30% during Diwali but he also bumped up the MP by 20%.

 

CONCEPT :

This is a profit and loss problem revolving around MP and discount. Here, we don’t need to calculate the CP.

 

ASSUMPTION :

Let’s take the initial MP = 100x

 

CALCULATION :

So, MP during Diwali = 100x × 120/100 = 120x

SP in Non-Diwali days = 100x × 70/100 = 70x

SP in Diwali days = 120x × 60/100 = 72x

Percentage change in SP = \(\frac{{\left( {72x - 70x} \right)}}{{70x}} \times 100 = \frac{{20}}{7} = 2.86\% \)

97438.

A shop owner offers the following discount options on an article to a customer:1. Successive discounts of 10% and 20%, and then pay a service tax of 10%2. Successive discounts of 20% and 10%, and then pay a service tax of 10%3. Pay a service tax of 10% first, then successive discounts of 20% and 10%Which one of the following is correct?1. 1 only is the best option for the customer.2. 2 only is the best option for the customer.3. 3 only is the best option for the customer.4. All the options are equally good for the customer.

Answer» Correct Answer - Option 4 : All the options are equally good for the customer.

Concept used:

Successive discount

Calculation:

Let the cost price of the article be x

For 1st type =  \({\rm{x}} \times \frac{{90}}{{100}} \times \frac{{80}}{{100}} \times \frac{{110}}{{100}} = {\rm{\;}}0.792{\rm{x}}\)

For 2nd type = \({\rm{x}} \times \frac{{80}}{{100}} \times \frac{{90}}{{100}} \times \frac{{110}}{{100}} = {\rm{\;}}0.792{\rm{x}}\)

For 3rd type = \({\rm{x}} \times \frac{{110}}{{100}} \times \frac{{80}}{{100}} \times \frac{{90}}{{100}} = {\rm{\;}}0.792{\rm{x}}\)

For every types effective discount is same

∴ Option 4 is the correct answer

97439.

An old man is having 3 children, Ronaldo, Messi and Neymar. He gave money to them to start a grocery shop. Ronaldo get Rs. 6000, Messi got Rs. 2000 and Neymar got Rs. 6000. Ronaldo left after six months. If after eight months there was a gain of Rs. 7500, then what will be the share of Messi?1. Rs. 45002. Rs. 55003. Rs. 65004. Rs. 12005. None of these

Answer» Correct Answer - Option 4 : Rs. 1200

Given

Ronaldo, Messi and Neymar got Rs. 6000, 2000 and 6000 to start a business after 8 months, there was a gain of = Rs. 7500

Formula used

Basic knowledge of Ratio.

Calculation

Ratio of Ronaldo, Messi and Neymar = (6000 × 6) ∶ (2000 × 8) × (6000 × 8)

= 36000 ∶ 16000 ∶ 48000

= 36 ∶ 16 ∶ 48 = 9 ∶ 4 ∶ 12

∴ Messi’s share = Rs. (7500 × 4/25) = Rs. 1200

After 8 months, Messi got Rs. 1200 out of Rs. 7500. 

97440.

A grocery shop owner usually makes a profit of 20% in a certain transaction. If he charges 20% less than what he usually charges and he used 900 gm weight instead of 1 kg. What is his actual profit or loss percentage?1. (10/3)%2. (20/3)%3. (40/3)%4. 20%

Answer» Correct Answer - Option 2 : (20/3)%

Given:

A grocery shop owner usually makes a profit of 20% in a certain transaction.

Formula used:

SP = CP × (100 + P%)/100

Profit% = (P/CP) × 100

SP = MP × (100 - D)/100

Where,

CP  → cost price

MP  → marked price

P → Profit 

D  → Discount

SP  → selling price

Calculations:

Let the cost of 1 kg of goods be Rs. 100 but shopkeeper charges Rs. 120 to the customer.

But now shopkeeper is giving only 900 grams to a customer that cost him at Rs. 90.

But he gives 20% discount on his previous selling price = (80/100) × 120 = Rs. 96.

Profit = 96 - 90 = 6 

Profit % = (6/90)×100 = (20/3)%

∴ His actual profit percentage is (20/3)%.

97441.

A fruit seller buys avocados at Rs.100, Rs. 80 and Rs. 60 per kilogram. He mixes them in the ratio 2 ∶ 4 ∶ 9 by weight and sells at a profit of 30%. At what approximate price /kg does he sell the dry fruit?1. Rs. 912. Rs. 923. Rs. 964. Rs. 94

Answer» Correct Answer - Option 2 : Rs. 92

Given:

A fruit seller buys avocados at Rs.100, Rs. 80 and Rs. 60 per kilogram.

Formula used:

Selling price (SP) = CP × (100 + P%)/100

Where, 

CP →  cost price 

P → Profit

Calculations:

Let the weight of avocados be 2x, 4x, and 9x.

So total weight = 2x + 4x + 9x = 15x kg

Cost of 15x kg of avocados = Rs. (100 × 2x) + (80 × 4x) + (60 × 9x) = Rs. 1060x

Thus selling price = CP × (100 + P%)/100 = 1060x × (130/100) = 1378x

SP of fruits per kg = 1378x/15x = 91.86 ≈ Rs. 92/kg

∴ The approximate price/kg he sells the dry fruit is Rs. 92.

97442.

A milk trader buys 50 liters of milk at the rate of Rs. 40 per liter and mixes 10 liters of water (water is free) in it. If he sells this mixture at the rate of Rs. 50 per litre, then what is the profit percentage?1. 50 percent2. 33.33 percent3. 60 percent4. 40 percent

Answer» Correct Answer - Option 1 : 50 percent

Given:

Cost price(CP) of milk = Rs. 40 per litre

Total quantity of milk purchased = 50 litre

Water added to the milk = 10 litre

Selling price(CP) of milk = Rs. 50 per litre

Formula used: 

Profit = SP - CP

Profit% = (Profit/CP) × 100

Calculation:

Total CP = 40 × 50 = 2000

Total SP = 50 × 60 = 3000

Profit = 3000 - 2000 = 1000

Profit% = (1000/2000) × 100 = 50

∴ Profit = 50%

97443.

What happens to molar conductivity when one mole of KCL dissolved in one liter is diluted to five liters?

Answer»

The answer is increases.

97444.

Iron is prepared from one of its ore hematite `Fe_(2)O_(3)` by reaction with carbon as follows: `Fe_(2)O_(3)(s)+C(s)rarrFe(s)+CO_(2)(g)uparrow` Above reaction occur in an open furnance. In above question number 8 how much carbon was consumed.A. 9gmB. 0.4kgC. 9kgD. 40kg

Answer» `n_(C) "consumed"=(3xxn_(Fe))/(4)=(3)/(4)xx10^(3)`
`w_(C) "consumed"=(3)/(4)xx12=9kg`
97445.

Iron is prepared from one of its ore hematite `Fe_(2)O_(3)` by reaction with carbon as follows: `Fe_(2)O_(3)(s)+C(s)rarrFe(s)+CO_(2)(g)uparrow` Above reaction occur in an open furnance. If carbon was taken in limiting quality, as a result finally 100kg of crude iron (a mixture of `Fe_(2)O_(3)` and Fe) was obtained. And crude iron has `56%` pure Fe. Then what mass of `Fe_(2)O` was taken initiallyA. 80kgB. 124kgC. 44kgD. 100kg

Answer» `2Fe_(2)O_(3)(s)+3C(s)rarr4Fe(s)+3CO_(2)`
after reaction 44kg 56 kg
`n_(Fe(2)O_(3))"used"=n_(Fe)=("formed")/(2)=(56)/(56)xx(10^(3))/(2)`
`w_(Fe_(2)O_(3))"used"=(160)/(2)kg=80kg`
`w_(Fe_(2)O_(3))` initially taken =80+44=124kg
97446.

Iron is prepared from one of its ore hematite `Fe_(2)O_(3)` by reaction with carbon as follows: `Fe_(2)O_(3)(s)+C(s)rarrFe(s)+CO_(2)(g)uparrow` Above reaction occur in an open furnance. Mass of Carbon required to produce 112kg of pure iron:A. 36kgB. 18kgC. 48kgD. 72kg

Answer» `2Fe_(2)O_(3)(s)+3C(s)rarr12Fe(s)+3CO_(2)(g)uparrow`
`n_(C)=(n_(Fe))/(4)xx3=(112)/(56)xx(3)/(4)`
`w_(C)=(112)/(56)xx(3)/(4)xx18kg`
97447.

12 Litres of `CO_(2)` gas is obtained on complete combustion of 5 litre gaseous mixture of ehtane and propane then what will be the percentage amount of ethane in mixture ?A. 0.6B. 0.4C. 0.5D. 0.75

Answer» Correct Answer - A
97448.

The freezing point of an aqueous solutions is 272 .93 K . Calculate the molality of the solution if molal depression constant for water is 1.86 Kg `mol^(-1)`

Answer» Correct Answer - Molality of the solution `=0.0376 m`
Given : For pure water `T_(o) = 273 K`
For solution `T_(r) = 273 .93 K`
`K_(r) = 1.86 K kg mol^(-1)`
Molality of the solution `= m= ?`
Depression in the freezing point `= Delta T_(f)= T_(o) - T_(f)= 273 - 272 .93 = 0.07 K`
`Delta T_(f) = K_(f) xx M`
`:. m = (Delta T_(f))/(K_(f)) = (0.07)/(1.86) = 0.0376 "mol" kg ^(-1)`
97449.

If mole fraction of solvent is ' \( s \) ' and lowering of vapour pressure is ' \( p \) ' mm of Hg then, what will be vapour pressure of pure solvent (Po)? (assume solute is nonvolatile and nonelectrolyte) (1) \( p^{\circ}=s p \) (2) \( p ^{\circ}= p ^{\prime} s \) (3) \( p^{\circ}=s / p \) (4) \( p^{0}=p /(1-s) \)

Answer»

Correct option is (4) Po = \(\frac{P}{1-S}\) 

As we know, relative lowering of vapour pressure is given by--

\(\frac{P^o-P_1}{P^o}=x\)----(1)

where,

Po - P1 = lowering in vapour pressure

Po = Vapour pressure of pure solvent

x = mole fraction of solute

we have given,

lowering of vapour pressure = P- P1 = P

mole fraction of solvent  = 'S'

∴ mole fraction of solute = 1 - S

putting these values in equation (1)

\(\frac{P}{P^o}=1-S\) 

Po = \(\frac{P}{1-S}\)

Po = \(\frac{P}{1-S}\) 

Therefore, vapour pressure of pure solvent will be

Po = \(\frac{P}{1-S}\) 

97450.

A ball of mass `m` is attached to a string whose other end is fixed. The system is free to rotate in vertical plane. When the ball swings, no work is done on the ball by the tension in the string. Which of the following statement is the correct explanation?A. Tension is always perpendicular to the direction of motion of the ball.B. Tension is an internal force for the ball.C. Tension is an external force for the ball.D. Since the ball is swinging about the axis, total displacement is zero.

Answer» Correct Answer - A
Tension acts rediially inward and velocity is tangetial so tension is always `bot` to the direction of motion of ball.