Chapter 1: Basic concepts in chemistry
In this article, the author has explained the most important chemistry MCQs from the first chapter( Basic concepts) of FSC chemistry. All the correct answers have been highlighted in blue color.
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1: What mass of oxygen is consumed by the complete combustion of 21.0 gram of ethylene?
a) 24.1 g
b) 72.0 g
c) 60.5 g
d) 69.0 g
2: If proton number of two atoms is same then it can be concluded that
a) They are isotopes
b) Compounds of both atoms will be similar in reactivity towards other compounds
c) Both have same colours
d) Both have same melting point
3: Empirical formula and formula unit of an ionic compound
a) May be similar or different
b) Are always different
c) are always similar
d) Ionic compounds don’t have any empirical formula
4: A compound contains two elements X and Y percentage of X is 20% ( At.wt = 40) and that of Y is 80% (At.wt = 80). The empirical formula of the compound is
a) X2Y
b) X3Y
c) XY
d) XY2
5: Which of the following statement is correct ?
a) The NO. of negative ions having group of atoms is less common
b) The NO. of peaks in mass spectrum shows the number of isotopes
c) Elements with odd atomic number possess more than two stable isotopes
d) The current strength of each isotope of an element gives mass number
6: Avogadro’s number is the number of molecules present in
a) Number of particles
b) 1 g of molecule
c) gram molecule mass
d) 1g atom of H2 gas
7: A mole of any substance is related to
a) Number of particles
b) Mass of a substance
c) Volume of gaseous substances
d) All of these
8: The number of gram molecules of oxygen in 6.02 x 1024 CO molecules is
a) 1g molecules
b) 5g molecules
c) 2 g molecules
d) 8 g molecules
9: Boron has two stable isotopes, B10, (19%) and B11 (81%). Find the average atomic weight of boron?
a) 11.2
b) 12.6
c) 10.8
d) 9.6
10: Which among the following is the heaviest?
a) one mole of oxygen
b) 100 amu of uranium
c) One molecule of sulfur trioxide
d) 44 g carbon dioxide
11: A compound possesses 8 % sulfur by mass. The least molecular mass is
a) 200
b) 155
c) 400
d) 355
12: The incorrect statement for 14 g of CO is
a) It occupies 2.24 liter at STP
b) It corresponds to 0.5 mol of CO
c) It corresponds to same mol of CO and N2
d) It corresponds to 3.01 x 1023
13: Which of the followings is not true for atom?
a) It can always exist independently
b) It is composed of subatomic particles
c) It can be ionized
d) It can combine with other atoms
14: From the complete decomposition of 20 g CaCO3 at STP the volume of CO2 obtained is
a) 2.24 L
b) 44.8 L
c) 4.48 L
d) 48.4 L
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15: The volume of 1.0 g of hydrogen in liters at STP is
a) 22.4 L
b) 11.2 L
c) 1.12 L
d) 44.56 L
16: Which has maximum number of molecules?
a) 7 g N2
b) 18 g NO2
c) 2 g H2
d) 16 g O2
17: In the reaction, 4NH3 + 5O2 ……….. 4NO + 6H2O, when one mole of ammonia and one mole of oxygen are made to react to completion, then
a) 1.0 mol of H2O is produced
b) 1.5 mol No is formed
c) All the oxygen is consumed
d) All the ammonia is consumed
18: The No. of unstable isotopes produced due to artificial means is
a) 300
b) 400
c) 250
d) None of above
19: In the mass spectrometer the atoms or molecules are ionized by using
a) alpha-particles
b) gamma-rays
c) Electrons
d) All of these
20: The maximum number of molecules is present in
a) 15 L of H2 gas at STP
b) 1.5 g of H2 gas
c) 5 L of N2 gas at STP
d) 5 g of O2 gas
21: For equal mass which of the following pairs of gases contain equal number of molecules?
a) CO2 and NO2
b) NO and CO
c) CO and CO2
d) N2O and CO2
22: x liter of carbon monoxide are present at STP. It is completely oxidized to CO2, the volume of CO2 formed is 11.207 liters at STP. What is value of X in liters?
a) 11.2
b) 10.2
c) 21.2
d) 32.2
23: The mass spectrum of an unknown element Z shows nine peaks. The element Z may be
a) Neon
b) Silver
c) Palladium
d) Cadmium
24: Given the following equation
2KClO3 ————- 2KCl + 3O2
The maximum mass of O2 produced by the decomposition of 0.3 NA formula units of KClO3 is
a) 14.4 g
b) 148 g
c) 48 g
d) None of these
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25: An atom is
a) Smallest invisible particle in an element
b) Smallest particle of an element which can undergo a chemical reaction
c) Building block of an element
d) Always smaller than molecule
26: 10 moles of H2O contains
a) 100 moles of bonds
b) 25 moles of hydrogen bonds
c) 30 atoms
d) 100 moles of electrons
27: The total number of moles of sulfur required to produce 100 moles of sulphuric acid is
a) 100
b) 50
c) 150
d) 200
28: Which of the following is not a use for mass spectrometry?
a) Calculating the isotopic abundance in elements
b) Investigating the elemental composition of planets
c) Confirming the presence of O-H and C=O in organic compounds
d) Calculating the molecular mass of organic compounds
29: 8 g of O2 reacts with 8 g of H2 to produce water. Which order is correct according to the limiting and non-limiting reactant respectively?
a) H2, O2
b) O2, H2
c) Both are limiting reactants
d) Both are non-limiting reactant
30: The number of atoms in 4.25 g of NH3 is approximately
a) 1 x 1023
b) 4 x 1023
c) 2 x 1023
d) 6 x 1023
31: The element showing single peak in mass spectrograph is
a) Fluorine
b) Bromine
c) Chlorine
d) Neon
32: Number of atoms in 560 g of Fe ( atomic mass 65 g/mol) is
a) is twice that of 70 g of N
b) is half as 2 grams of hydrogen
c) Is half that of 20 g H
d) None of these
33: An acid of molecular mass 104 contains 34.6 % carbon and 3.8 % hydrogen and the rest is oxygen. The molecular formula of the acid is
a) C3H4O4
b) C2H4O2
c) C2H2O4
d) None of above
34: How many moles of magnesium phosphate, Mg3(PO4)2 will contain 0.25 mole of oxygen atoms?
a) 0.02
b) 1.25 x 10-2
c) 3.125 x 10-2
d) 2.5 x 10-2
35: What is the number of atoms in 224 dm3 of chlorine gas at STP
a) 10
b) 20
c) 6.02 x 1024
d) 1.2 x 1025
36: 4 moles of oxygen atoms are present in
a) 4.0 moles of H2SO4
b) 2 moles of H2SO4
c) 0.5 moles of H2SO4
d) None of above
37: 7.5 gram of a gas occupies 5.6 liters as STP. The gas is
a) CO
b) NO
c) CO2
d) N2O
38: If equal moles of glucose and urea are taken in a vessel fillied with waer what will be the mass percentage of urea in the solution?
a) 75
b) 50
c) 46.146
d) 25
39: One mole of CH4 contains
A) 4 g atoms of hydrogen
B) 6.02 x 1023
c) 3 g atoms of carbon
d) 1.810 x 1023 molecules of CH4
40: A gold ( Ar=197) pendant weighs 1.97 grams. The number of atoms it contains is
a) 6.02 x 1023
b) 3.01 x 1022
c) 6.02 x 1021
d) 6.02 x 1022
41: 0.25 mol of P4 molecules contains …….. atoms?
a) 1.764 x 1023
b) 6.023 x 1023
c) 6.02 x 1019
d) 8.086 x 1023
42: If 6.40 g of an unknown molecular species contains 12.04 x 1022 molecules, the species if;
a) O2
b) N2
c) CO2
d) SO2
43: Dinitrogen trioxide, a blue solid, dissociates to form nitrogen monoxide and nitrogen dioxide gases. What mass of nitrogen is formed from the decomposition of 19.01g of N2O3?
a) 5.17g
b) 6.55g
c) 7.93g
d) 12.0g
44: Bismark brown is a dye. Its molar mass is 228g/mol. When the dye was analyzed by a scientist, it was found that it contains 30.68% nitrogen. How many nitrogen atoms are there in each Bismark brown molecule?
a) 6
b) 5
c) 4
d) 3
45: Which has maximum number of molecules?
a) 7g N2
b) 18g NO2
c) 2g H2
d) 16g O2
46: The electrometer of the mass spectrometer is also called
a) Ion collector
b) Ion counter
c) Electron counter
d) Ionometer
47: Which formula shows highest percentage of nitrogen of nitrogen by mass
a) NH3
b) N2H4
c) NO2
d) NH4OH
48: An ion is formed when
a) An electron is added to an atom.
b) An electron is removed from an atom.
c) An electron is removed from a molecule.
d) All of the above
49: When an electron is taken up by a non-metal atom, energy is
a) Released
b) Remains constant
c) Absorbed
d) May release or absorb
50: Ions and the atoms from which they are formed above
a) Same chemical properties
b) Almost same masses
c) Same no. of electrons
d) All of these
51: Which one of the following pair has the same empirical and molecular formula?
a) C6H6, NaCl
b) C6H12O6, C12H22O11
c) CO2, H2O
d) NH3, C6H6O2
52: Percentage of oxygen in H2O is
a) 80%
b) 8.8%
c) 88.8%
d) 9.8%
53: The least number of H+ are produced by complete ionization of
a) 0.100 moles of HCl
b) 0.334 moles of H3PO4
c) 0.05 moles of H2SO4
d) All of the above
54: Total no. of electrons present in 48g Mg2+ are
a) 24NA
b) 20NA
c) 2NA
d) None of these
55: A sample of pure matter is
a) Element
b) Substance
c) Compound
d) Mixture
56: How many moles of CO2 which contains 8.0 gm of oxygen
a) 0.25
b) 1.0
c) 0.50
d) 1.50
57: Which of the following is not correctly matched about the applications of a mass spectrometer
a) No. of atomic ions peaks : no. of isotopes
b) Height of peaks : Relative abundance of isotopes
c) m/e ratio : mass of isotopes
d) Position of atomic ion peaks on abscissa : Isotopic mass
58: How many moles of atoms are present in 7 moles of sulfuric acid?
a) 49
b) 21
c) 7 x 6 x 1023
d) 7
59: Compared to 88g of carbon dioxide, 88g of propane contains
a) Less atoms
b) The same number of molecules
c) The same number of atoms
d) More molecules
60: which of the following contain only empirical formulas?
a) C3H6, NO2, H2O2
b) C5H12, NO2, H2O
c) C5H10, N204, H2O2
d) C3H8, N204, H2O