Sample QuestionsMole concept and Stoichiometry questions
One sample from each question group in this chapter. Select any group above to see the full set with answer keys.
Which of the following contains maximum number of molecules?
- A
4 g of $O _2$
- ✓
4 g of $NH _3$
- C
4 g of $CO _2$
- D
4 g of $SO _2$
Answer: B.
View full solution →The number of molecules in 4.25 g of ammonia is :
- A
$1.0 x 10^{23}$
- ✓
$1.5 x 10^{23}$
- C
$2.0 x 10^{23}$
- D
$3.5 x 10^{23}$
Answer: B.
View full solution →Four grams of caustic soda contains :
Answer: C.
View full solution →Assertion: The reactant which is present in lesser amount parameters the amount of product formed is called limiting reagent.
Reason: Amount of product formed does not depend upon the number of reactants taken.
- A
Assertion and Reason both are correct statements and reason is the correct explanation of the assertion
- B
Assertion and Reason both are correct statements, but reason is not the correct explanation of the assertion
- C
Assertion is true, but reason is false.
- D
Assertion is false, but reason is true.
View full solution →The simplest formula of a compound containing $50 \%$ of element $X$ (atomic mass 10 ) and $50 \%$ of element $Y$ (atomic mass 20) is:
- A
$X Y$
- B
$X _2 Y$
- C
$X Y_3$
- D
$X _2 Y _3$
View full solution →560 ml of carbon monoxide is mixed with 500 ml of oxygen and ignited. The chemical equation for the reaction is as follows:
$2CO + O_2 \rightarrow 2CO_2$
Calculate the volume of oxygen used and carbon dioxide formed in the above reaction.
View full solution →Calculate the percentage of sodium in sodium aluminium fluoride $(Na_3AlF_6)$ correct to the nearest whole number.
$(F = 19; Na =23; Al = 27)$
View full solution →An Experiment showed that in a lead chloride solution, $6.21$ g of lead is combined with $4.26$ g of chlorine. What is the empirical formula of this chlorine? $( Pb =207 ; Cl =35.5)$
View full solution →When heated, potassium permanganate decomposes according to the following equation :
$2 KMnO _4 \longrightarrow K _2 MnO _4+ MnO _2+ O _2$
solid residue
(a) Some potassium permanganate was heated in the test tube. After collecting one litre of oxygen at room temperature, it was found that the test tube had undergone a loss in mass of $1.32 g$. If one litre of hydrogen under the same conditions of temperature and pressure has a mass of $0.0825 g$, calculate the relative molecular mass of oxygen.
(b) Given that the molecular mass of potassium permanganate is 158 . What volume of oxygen (measured at room temperature) would be obtained by the complete decomposition of $15.8 g$ of potassium permanganate? (Molar volume at room temperature is 24 litres)
View full solution →The percentage composition of sodium phosphate as determined by analysis is $42.1 \%$ sodium, $18.9 \%$ phosphorus and $39 \%$ oxygen. Find the empirical formula of the compound?
View full solution →A compound is formed by $24g$ of $X$ and $64g$ of oxygen. If the atomic mass of $X=12$ and $O=16$, calculate the simplest formula of the compound.
View full solution →Urea $[CO(NH_2)_2]$ is an important nitrogenous fertilizer. Urea is sold in 50 kg sacks. What mass of nitrogen is in one sack of urea?
View full solution →Some of the fertilizers are sodium nitrate $NaNO _3$, ammonium sulphate $\left( NH _4\right)_2 SO _4$ and urea $CO \left( NH _2\right)_2$. Which of these contains the highest percentage of nitrogen?
View full solution →(a) Calculate the number of moles and the number of molecules present in $1.4 \ g$ of ethylene gas. What is the volume occupied by the same amount of ethylene?
(b) What is the vapour density of ethylene?
View full solution →From the equation for burning of hydrogen and oxygen $2 H _2+ O _2 \longrightarrow 2 H _2 O$ (Steam)
Write down the number of mole (or moles) of steam obtained from 0.5 moles of oxygen.
View full solution →Calculate the number of moles in 7g of nitrogen.
Ordinary chlorine gas has two isotopes ${ }^{35}{ }_{17} Cl$ and ${ }^{37}{ }_{17} Cl$ in the ratio of $3: 1$. Calculate the relative atomic mass of chlorine.
View full solution →A gas cylinder filled with hydrogen holds $5 g$ of the gas. The same cylinder holds $85 g$ of gas $X$ under the same temperature and pressure. Calculate :
The molecular weight of gas $X$.
View full solution →A gas cylinder filled with hydrogen holds 5g of the gas. The same cylinder holds 85 g of gas X under the same temperature and pressure. Calculate :
Vapour density of gas X.
Calculate the percentage of phosphorus in Calcium phosphate $Ca _3\left( PO _4\right)_2$
View full solution →Complete the following blanks in the equation as indicated.
$CaH_2(s) + 2H_2O (aq) → Ca(OH)_2(s) + 2H_2(g)$
(c) Molecules: $6.02 \times 10^{23}$ + -------→-------- + ---------
View full solution →Complete the following blanks in the equation as indicated.
$CaH_2(s) + 2H_2O (aq) → Ca(OH)_2(s) + 2H_2(g)$
(b) Grams: $42g$ + ------- → -------- + ----------------
View full solution →Complete the following blanks in the equation as indicated.
$CaH_2(s) + 2H_2O (aq) → Ca(OH)_2(s) + 2H_2(g)$
(a) Moles: $1$ mole + ------- → -------- + --------------
View full solution →The volume occupied by one mole of a gas at S.T.P is____________
The number of atoms present in one molecule of a substance is its____________
The following experiment was performed in order to determine the formula of a hydrocarbon. The hydrocarbon $X$ is purified by fractional distillation.
$0.145 g$ of $X$ was heated with dry copper (II) oxide and $224 cm ^3$ of carbon dioxide was collected at S.T.P.
(a) Which elements does X contain?
(b) What was the purpose of copper (II) oxide?
(c ) Calculate the empirical formula of $X$ by the following steps:
(i) Calculate the number of moles of carbon dioxide gas.
(ii) Calculate the mass of carbon contained in this quantity of carbon dioxide and thus the mass of carbon in sample $X$.
(iii) Calculate the mass of hydrogen in sample X.
(iv) Deduce the ratio of atoms of each element in $X$ (empirical formula).
View full solution →Find the molecular formula of a hydrocarbon having vapour density $15,$ which contains $20\%$ of Hydrogen.
View full solution →Water decomposes to $O _2$ and $H _2$ under suitable conditions as represented by the equation below:
$2 H _2 O \rightarrow 2 H _2+ O _2$
(a) If $2500 cm ^3$ of $H _2$ is produced, what volume of $O _2$ is liberated at the same time and under the same conditions of temperature and pressure?
(b) The $2500 cm ^3$ of $H _2$ is subjected to $2$ times an increase in pressure (temp. remaining constant). What volume of $H _2$ will now occupy?
(c) Taking the value of $H _2$ calculated in $5$(b), what changes must be made in Kelvin (absolute) temperature to return the volume to $2500 cm ^3$ pressure remaining constant.
View full solution →The volume of gases $A, B, C$, and $D$ are in the ratio, $1: 2: 2: 4$ under the same conditions of temperature and pressure.
(i) Which sample of gas contains the maximum number of molecules?
(ii) If the temperature and pressure of gas A are kept constant, then what will happen to the volume of $A$ when the number of molecules is doubled?
(iii)If this ratio of gas volume refers to the reactants and products of a reaction, which gas law is being observed?
(iv)If the volume of A is actually $5.6 dm ^3$ at S.T.P., calculate the number of molecules in the actual Volume of D at S.T.P. (Avogadro's number is $6 \times 10^{23}$ ).
(v) Using your answer from (iv), state the mass of $D$ if the gas is dinitrogen oxide $\left( N _2 O \right)$
View full solution →The gases hydrogen, oxygen, carbon dioxide, sulphur dioxide, and chlorine are arranged in order of their increasing relative molecular masses. Given 8 g of each gas at S.T.P., which gas will contain the least number of molecules and which gas the most?