Test
Questions on Chapter # 1 ………….. Stoichiometry (Test # 2)
Short Question Answers
Q1. Define the following terms:
mole, molar volume, molar mass, a.m.u, Avogadro’s number, Stoichiometry, limiting reactant, stoichiometric amount, excess
reactant, mass-mass relationship, Avogadro’s law, Gay Lussac’s law,.
IMPORTANT NUMERICALS on
Mole Concept from BOOK
Q1. Calculate
the
(i) Mass of AgCl formed
(ii) Volume of H2S produced at
STP
(Molar
mass of Ag is 108 g/mol and S is 32 g/mol)
[Answer;
28.7 g and 2.24 dm3]
Q2. Calculate
the number of moles and molecules in
(i) 38 g of carbon disulphide (CS2) [Answer;
0.5 mole and 3.01 x 1023]
(ii) 68.4 g of sucrose (C12H22O11) [Answer; 0.2 mole and 1.24 x 1023]
Q3. 1.6 g of a
sample of gas occupies a volume of 1.12 dm3 at STP. Determine the
molar mass of the substance.
[Answer; 32 g/mol]
Q4. What volume
of oxygen gas (O2) occupied by 1.5 moles at STP. (Answer; 33.6 dm3)
Q5.Calculate the mass of 3.25 moles of
water (H2O). (Answer; 58.5 g)
Q6. Calculate
the number of molecules in 610 g of benzoic acid (C7H6O2).
(Answer; 3.01 x 1024 molecules)
Q7. Calculate the number of moles in 25.5 g
of sodium metal. (Answer; 1.11 moles)
Q8. Calculate
the number of moles in 2.35 x 1025 atoms of aluminium (Al). (Answer; 39 moles of Al)
Q9. Calculate
the mass of 4.39 x 1024 atoms of gold (Au), molar mass of gold is
193 g/mol.
(Answer; 12.365 g of
gold)
Q10. Graphite is one of the two crystalline
forms of carbon which is a constituent component of lead pencils. How many
atoms of carbon are there in 360 g of graphite? Also find the number of moles
of carbon. (Answer; 1.806 x 1025
atoms of C, 30 moles of C)
IMPORTANT NUMERICALS on
Mole Concept from External Source
Q1. Calculate
each of the following quantities
(i) Number of moles in 6.4 g of SO2 [Answer; 0.1 mol]
(ii) Mass in gram of 4.5 moles of ethyne (C2H2) [Answer; 117 g]
(iii) Volume in cm3 of 38.4 g O2
gas at STP [Answer; 26880 cm3]
(iv) Number of molecules of 126 g water [Answer; 4.214 x 1024]
(v) Mass in gram of 4.8 x 1024
atoms of sodium [Answer; 183.39 g]
(vi) Number of formula units in 333 g of CaCl2 [18.06 x 1023]
Q2. Solve the following:
(i) How many moles are there in 10 g of coke? (Ans; 0.833 mole)
(ii) Calculate the number of moles in 1.505
x 1022 atoms of Mg. (Ans; 0.025 mole)
(iii)
Calculate the mass in grams
of 3.01 x 1023 atoms of Zinc. (Ans; 32.7 g)
(iv) Calculate the number of atoms in 9.2
grams of Natrium. (Ans; 2.408 x 1023 atoms)
(v) Calculate the number of molecules in 0.8 moles of Glucose.(Ans;4.816x 1023 molecules)
(vi) How many molecules are there in 5.4 grams of water? (Ans;1.806x 1023 molecules)
(vii) In a collection of 24 x 1025 molecules of C2H5OH,
what is the number of moles? (398.6)
Q3. The sample of Chlorine gas at S.T.P. has a volume of 800 cm3. Calculate the mass of the sample and the number of molecules in the sample.
(Ans; 2.2536 g; 2.15 x 1022
molecules)
Q4. What
is the mass of 3.01 x 1023 molecules of N2? [K.B – 2007] (Ans; 1.4 g)
Q5. Calculate
the weight in grams of 3.01 x 1020 molecules of glucose. (Ans; 0.0899 g)
Q6. The
atomic mass of sodium is 23 amu. Calculate:
(a)The mass of 2.408 x 1023 atoms of Na. (Ans; 9.2 g)
(b) The
number of moles of Na in 4.6 g. (Ans; 0.2 mole)
Q7. Calculate
the mass in grams of 3.01 x 1023 molecules of water. (Ans; 9 g)
Q8. Calculate the
number of moles, the number of molecules and the volume in cm3 at
stp of 0.32 g of:
(i) CH4 gas (Ans; 0.02 mole, 1.204 X 1022 molecules, 448 cm3)
(ii) SO2 gas (Ans; 0.005 mole, 3.01X 1021 molecules, 112 cm3)
Q9. Calculate
the number of moles and the number of molecules present in 9.0 g of glucose.
(Ans; 0.5 mole, 3.011 X 1023 molecules)
Q10. The formula weight of NaOH is 40 amu. Find
(i) Its gram formula) weight. (Ans; 40 g)
(ii)Weight of 3 formula unit in amu. (Ans; 1.99 x 10-22)
(iii)Weight of 60200 formula unit in g. (Ans; 4 x 10-18 g)
(iv) Weight of 6 gram mole. (Ans; 240 g)
Q11. What is the mass of following in gram?
(i) One
atom of Silver (Ans: 1.79 x 10–22 g)
(ii) One atom of Cu (Ans: 1.05 x 10–22 g)
(ii) One
atom of Zn (Ans: 5.43 x 10–22 g)
(iv) One
atom of Gold (Ans: 3.27 x 10–22 g)
(v) One
atom of Iron (Ans: 9.3 x 10–22 g)
(v)One
atom of Carbon (Ans: 9.3 x 10–22 g)
Q12. 10 g
of H2SO4 has been dissolved in excess of water to
dissociate it completely into its ions. Calculate
(i) Number
of molecules in 10 g of H2SO4 (Ans: 6.14 x 1022 molecules)
(ii) Number
of positive ions (Ans: 1.2 x 1023 molecules)
[Hint; No of positive ions = Number of molecules x basicity of Acid]
IMPORTANT NUMERICALS on Stoichiometry from BOOK
Q1. Calculate the mass of carbon dioxide
(CO2) that can be obtained by complete thermal decomposition of 50 g
of lime stone (CaCO3)
CaCO3(s) →
CaO(s) + CO2(g)
(Answer; 22 g )
Q2. Mass of 49 g
of solid potassium chlorate (KClO3) on heating decomposes completely
to potassium chloride
(KCl) with the liberation of oxygen gas(O2)
2KClO3
→ 2KCl + 3O2
Determine
volume of oxygen gas (O2) liberated at STP.
(Answer;
13.44 dm3)
Q4. Silver sulphide (Ag2S) is an
anti microbial agent. In an experiment, 24.8g Ag2S is reacted with
the excess of hydrochloric acid as given in the following reaction:
Ag2S(s)
+
2HCl(aq) → 2AgCl(s) + H2S(g)
Calculate
the
(i) Mass of AgCl formed [Answer; 28.7 g]
(ii) Volume of H2S produced at
STP [Answer; 2.24 dm3]
(Atomic
mass of Ag is 108 and S is 32)
Q5. On heating solid ammonium nitrate (NH4NO3),
it decomposes to produce nitrous oxide (N2O) and water
NH4NO3(s)
→ N2O(g) + 2H2O(l)
If 200 g of ammonium
nitrate is completely consumed in the reaction, calculate the:
(i) mass of water formed
(ii)
Volume of N2O gas liberated at STP
(Answer; 90 g water, 56 dm3
of O2)
Q6. Calculate the volume of carbon dioxide
at StP that can be produced by
the complete burning of 50 dm3 of butane gas (C4H10)
in the excess of supply of oxygen gas (O2).
2C4h10(g) + 13O2(g) → 8CO2(g) +
10H2O(g)
(Answer; 200 dm3)
IMPORTANT NUMERICALS on
Stoichiometry from External Source
Q1. Calculate the volume of CO2
gas produced at standard temperature and pressure by combustion of 50 g of
methane. CH4 + 2O2 → CO2 + 2H2O
(Ans; 70 dm3)
Q2.Calculate the volume
of O2 at S.T.P. produced by the complete decomposition of 540 g of N2O5
2N2O5 → 4NO2 + O2
(Ans; 56 dm3)
Q3. 100 grams of KNO3 are heated
to redness. What volume of oxygen at 39°C and 765 mm pressure will evolve? (Karachi
Board-2006)
2KNO3 → 2KNO2 + O2
(Ans; 11.089 dm3)
Q4. Potassium
chlorate if often used to generate oxygen gas in high school laboratory. If
183.7 g of KClO3 is completely burnt catalytically, what volume of
oxygen gas will be obtained at 39○C and 1200 torr pressure?
2KClO3 → 2KCl + 3O2
Q5. Calculate
the volume of nitrogen gas produced by heating 800 g of ammonia at 21°C and 823 torr pressure?
2NH3 → N2 + 3H2 (KB- 2014)
(Ans; 522.19 dm3)
Q6. CaCO3
is often used to generate CO2 gas in industry. If 200 g of CaCO3
is strongly heated, what volume of CO2 gas will be obtained at 30°C and 1200 torr pressure? (KB- 2017)
CaCO3(s) → CaO(s) + CO2(g)
(Ans; 31. 49 dm3)
Q7. Zinc reacts with H2SO4
(dil) as given below:
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
Calculate the mass of ZnSO4, the volume of H2 gas at STP and the number of molecules of H2 gas which will be produced by reacting 163.5 g of Zn with H2SO4.
(Ans;403.5 g of ZnSO4, 56 dm3 of H2
gas, 1.505 x 1024 molecules of H2 gas)
IMPORTANT NUMERICALS on
Limiting Reactant from BOOK
Q1. How many grams of NH3 are
formed when 100 g of each of the following reagents are reacted together
according to following equation;
2NH4Cl(s) + Ca(OH)2(s) → CaCl2(s) +
2NH3(g) + 2H2O(l)
(Ans; 31.62 g)
Q2. 5.6
g of NH3 are allowed to react with 4.5 g of O2 according
to following equation. Calculate number of moles, number of molecules, mass in
gram and volume in cm3 of nitric oxide evolved at STP.
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
(Ans; 0.1128 mol NO, 6.79 x 1023 molecules of
NO, 3.384 g NO, 2526.72 cm3 NO)
Q3. Combustion of ethene in air to form CO2
and H2O is given in the following equation
C2H4(g) +3O2(g) → 2CO2(g) + 2H2O(l)
If a mixture containing 2.8 g C2H4 and 6.4 g O2 is allowed to ignite, identify the limiting reactant anddetermine the mass of CO2 gas will be formed.
(Answer; 5.852 g)
Q4. Ammonia gas
can be produced by heating together solid NH4Cl and Ca(OH)2
2NH4Cl
+ Ca(OH)2 → CaCl2 + 2NH3 + 2H2O
If a mixture containing 100 g of each these solids is heated, determine the limiting reactant and mass of NH3 gas produced
[Answer; Limiting reactant is NH4Cl, Mass of NH3 is 31.7 g]
IMPORTANT NUMERICALS on
Yield of Reaction from BOOK
Q1.The reaction of calcium carbonate (CaCO3)
with hydrochloric acid is given as
CaCO3(s) + 2HCl(aq) → CaCl2 + CO2(g) + H2O(l)
If during an experiment 50 g of CaCO3 is reacted with excess of hydrochloric acid, 14.52 g of CO2 is liberated, calculate the theoretical and percentage yield of CO2 gas.
[Ans: 66%]
Q2. Under high pressure magnesium (Mg) reacts with oxygen (O2) to form magnesium oxide (MgO). 2Mg + O2 → 2MgO
If 4 grams of Mg reacts with excess of O2 to produce 4.24 g of MgO, calculate the percentage yield of MgO.
[Ans: 63.85%]
Q3. Aluminium chloride is used in the
manufacturing of rubber. It is produced by allowing aluminium to react with Cl2 gas at
650oC.
2Al(s) + 3Cl2(g) → 2AlCl3(l)
When 160 g aluminium reacts with excess of chlorine, 650 g of AlCl3 is produced. What is the percentage yield of AlCl3?
[Ans: 82.17%]
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