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 substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Equal volumes of iron and aluminum have different masses because they have different _________ .

  1. shapes

  2. densities

  3. lengths

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

If volume of iron = Volume of aluminium

then mass of iron > mass of aluminium
$\rho _{iron}\times V _{iron} > \rho _{aluminium}\times V _{aluminium}$
$\rho _{iron} > \rho _{aluminium}$

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

A metal forms two oxides. The higher oxide contains $80\%$ metal. $0.72 g$ of the lower oxide gave $0.8 g$ of higher oxide when oxidized. Then the ratio of the weight of oxygen that combines with the fixed weight of the metal in the two oxides will be:

  1. $2 :3$
  2. $2: 1$
  3. $4 :5$
  4. $3 : 2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Given that ,in higher oxide 80% metal is true.
wt. of metal$=\dfrac { 80 }{ 100 } \times 0.8\\$       
                    $ =0.64gm\\ $
wt. of oxygen$=0.16gm$
in lower oxide,
wt. of metal will be same as that of higher oxidation state(+2)

wt. of oxygen$=(72-0.64)=0.08g$

so,ratio of weight of $O _2$ & meals in two oxide is $0.16:0.08=2:1$.
1000ml of 0.75 M HCl = 0.75 mol

So, 25 ml of HCl will contain HCl = $0.75 \times 25 /1000$  = 0.01875

2 mol of HCl reacts with 1 mol of $CaCO _3$

So, 0.01875 mol of HCl will react with $\frac{1}{2}$ $\times$ 0.01875  = $0.009375$ mol

Molar mass of $CaCO _3$ = 100 g

Hence, the mass of 0.009375 mol of $CaCO _3$  = no. of moles $\times $ molar mass$
                                                                          
 $0.009375$ $\times100$  
                                                                   
Hence, the correct option is $C$.
Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Two oxides of a metal contain $50$% and $40$% metal (M) respectively. If the formula of first oxide is $MO _2$, the formula of second oxide will be:

  1. $MO _2$
  2. $MO _3$
  3. $M _2O$
  4. $M _2O _5$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
$\text{Compound } 1\quad\quad\quad\quad 50\% M+50\% O$
$\text{formula}\quad\quad\quad\quad MO _2$
Let atomic weight of metal be $X,$
$\Longrightarrow MO _2:$    $\cfrac{16}{X}=\cfrac{1}{2}$
Hence atomic weight of metal $=32$
$\text{Compound }2:$ $40\% M=\cfrac{40}{32}=1.25=1\\60\%O=\cfrac{60}{16}=3.75=3$
$\therefore$ Formula is $MO _3$.
Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Two oxides of a metal contain 72.4% and 70% of metal respectively? If formula of 2nd oxide is $ M _{2}O _{3} $, find that of the first ?

  1. MO
  2. $ M _{3}O _{4} $
  3. $ M _{3}O _{2} $
  4. $ MO _{2} $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For the second oxide M2O3, 70% is metal, so 30% is oxygen. The ratio of moles M:O is (70/M) : (30/16) = 2:3. Solving gives M = 56 (Iron). For the first oxide (72.4% metal), ratio is (72.4/56) : (27.6/16) = 1.29 : 1.725 = 3:4. Thus, M3O4.

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

One mole of glucose on metabolism, liberate how many kilo calories of energy ?

  1. 180

  2. 80

  3. 160

  4. 380
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

On complete combustion of glucose (1 mole) to CO$ _{2}$ & H$ _{2}$O, approx. 686 kcal of energy is released. When 1 g of glucose respires aerobically by ETS, Glycolysis and  Krebs cycle, around 38 ATP molecules are generated. The terminal group of a mole of ATP has around 10 kcal. Thus, 38 ATP molecules represent a yield of 380 kcal of energy.  

So the correct option is '380'

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

Complete oxidation of 1 gm mol of glucose gives rise to ................. calories.

  1. 6860000

  2. 686000

  3. 68600

  4. 6860

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

At pH 7.0 and temperature 298 K, the standard free energy change of oxidation of glucose is -686 Kilocalories per mole or -2840 Kilojoules per mole. The negative values indicate that oxidation of glucose is an exergonic or energy releasing process.

Multiple choice chemistry rocks and minerals coal petroleum non-renewable sources of energy

Molecular weight of crude petroleum may be around:

  1. $500$
  2. $1000$
  3. $2500$
  4. $1500$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Crude petroleum is the multi component mixture consisting of many compounds. It is drilled from the earth's crust and then refined in the petroleum refineries. Its molecular weight is around $1500$.

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

Four students found set of $C _{p}$ and $C _{v}$[in cal/deg mole] as given below, which of the following set is correct 

  1. $C _{v}=4,C _{p}=2$
  2. $C _{v}=4,C _{p}=3$
  3. $C _{v}=3,C _{p}=4$
  4. $C _{p}=5,C _{v}=3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

C$ _{v}$ cannot be greater than $C _{p}$

Hence, option A  and option B are incorrect.

We have the relation $C _{p} - C _{v}$= R ( and its value is 2 cal/mole ) and hence option C is also incorrect.