Chemistry

Mole Concept and Stoichiometry

354 Questions

The mole concept is a core area of chemistry focusing on the quantitative relationships between reactants and products in chemical reactions. Questions cover molecular mass calculations, stoichiometric conversions, and determining the number of molecules. This topic is essential for most science entrance and competitive examinations.

molecular mass calculationsstoichiometric conversionsmole fraction problemsheavy water reactionsoxidation calculations

Mole Concept and Stoichiometry Questions

Multiple choice chemistry nitrogen and sulfur ammonia-properties and uses ammonia compounds of nitrogen - ammonia

The atomic weight of zinc is $65.4$. The volume of dry hydrogen at NTP liberated by treating $6.54\ g$ of zinc with dilute sulphuric acid would be:

  1. $22.4$ litres
  2. $11.2$ litres
  3. $2.24$ litres
  4. $1.12$ litres
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Zn+H _2SO _4 \rightarrow ZnSO _4+H _2$

The volume of 1 mol of gas at N.T.P. is 22.4 litres. Moles of zinc used is equal to moles of hydrogen liberated.
Moles of zinc used is $\dfrac{6.54}{65.4}$=0.1 mol
Thus volume of hydrogen formed is $ 0.1 \times 22.4$=$2.24$ litres

Multiple choice maths calculations and mental strategies 1 equations from statements forming equations from statements writing mathematical statements

In an alloy of zinc, tin and lead, quantity of zinc is $\left(\cfrac{3}{4}\right)^{th}$ that of tin and quantity of tin is $\left(\cfrac{4}{5}\right)^{th}$ that of lead. How much of each metal will be there in $12$ kg of the alloy?

  1. $5,4,3$
  2. $3,4,5$
  3. $4,5,3$
  4. $5,3,4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Let the quantity of the tin be $'x'$ , zinc be $'y'$ and lead be $'z'$.
Given quantity of zinc is $\cfrac{3}{4}th$ of tin,
$\implies y=\cfrac{3}{4}(x)--------(1)$
Quantity of tin is $\cfrac{4}{5}th $ of lead,
$\implies x=\cfrac{4}{5}(z)------(2)$
But given total weight $=12kg$
$\implies x+y+z=12$
From $(1)&(2) $equations
$x+\cfrac{3}{4}x+\cfrac{5x}{4}=12$
$\cfrac{12x}{4}=12$
$\implies x=4$
if $x=4, y=3,z=5$
So the quantity of tin is $4kg$ , zinc is $3kg$ , lead is $5kg$

Multiple choice

RQ of tripalmitin is

  1. 0.7

  2. 0.9

  3. 0.8

  4. All
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Respiratory Quotient (RQ) for tripalmitin (a fat) is approximately 0.7, as fats require more oxygen for oxidation relative to the CO2 produced.

Multiple choice botany metabolism, cell respiration, and photosynthesis light dependent or hill reaction phases of photosynthesis emerson's experiments & hill's reaction

How much oxygen is formed from 264 g of $CO _2$ and 216 g of $H _2O$?

  1. 96 g

  2. 216 g

  3. 264 g

  4. 192 g.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Moles = Weight in gms/molecular weight
So, moles of CO$ _2$ =264/44 = 6 moles.
  • In same way moles of H2O = 216/18 = 12 moles.
In a reaction of photosynthesis, 6 moles of CO$ _2$ and 6 moles of water lead to the production of 6 moles of oxygen. Here, CO$ _2$ is a limiting reactant. So only 6 moles of oxygen will be formed.So, 6 moles of O$ _2$ = weight in gms/32 (molecular weight of O$ _2$). Weight in gms = 6 x 32 = 192 gms.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

$30\ g$ of Magnesium and $30\ g$ of oxygen are reacted, then the residual mixture contains:

  1. $50\ g$ of Magnesium oxide and $10\ g$ of oxygen
  2. $40\ g$ of Magnesium oxide and $20\ g$ of oxygen
  3. $45\ g$ of Magnesium oxide and $15\ g$ of oxygen
  4. $50\ g$ of Magnesium only
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$2Mg+ { O } _{ 2 } \rightarrow 2 MgO$
According to the above reaction,
$28.6 g (2 mole)\ Mg$ combine with $32 g (1mole)$ of ${ O } _{ 2 }$ to give $80.6g(2mole)$ of MgO.
thus,
$30 g\ Mg$ will combine with $20 g$ of ${ O } _{ 2 }$ to produce $50 g\ MgO$ and $10 g$ ${ O } _{ 2 }$will remain unreactive.
Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Total how many hydrogen atoms are present in one molecule of triple superphosphate?

  1. 6

  2. 8

  3. 9

  4. 12
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Monocalcium phosphate is an inorganic compound with the chemical formula $Ca{ ({ H } _{ 2 }P{ O } _{ 4 }) } _{ 2 }$. It is commonly found as the monohydrate $Ca{ ({ H } _{ 2 }P{ O } _{ 4 }) } _{ 2 }.{ H } _{ 2 }O$ Both salts are colourless solids. They are used mainly as superphosphate fertilizers.

So a total of 6 hydrogen atoms are present.

Multiple choice chemistry chemical formula and mole concept introduction to mole gas laws and mole concept mole concept

A gaseous oxide contains 30.4% of nitrogen, one molecule of which contains one nitrogen atom. The density of the oxide relative to oxygen is:

  1. 0.94

  2. 1.44

  3. 1.50

  4. 3.0
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

100g of oxide contain 30.4 g of Nitrogen. 


Since 1 molecule contain one nitrogen atom

14 g Nitrogen is contained by Mol. wt of oxide.

30.4 g of nitrogen present in 100 g of oxide 

$ 1 g ------------\dfrac{100}{30.4} $

$ 14 g-------------\dfrac{100 \times 14}{30.4} $

$ \dfrac{doxide}{doxygen}=\dfrac{Moxide}{Moxygen}=\dfrac{\dfrac{1400}{30.4}}{32}=1.44 $