Engineering Entrance
Q. How many molecules are in 0.25 moles of oxygen gas (O2)? (2022)
-
A.
3.011 x 10^23
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B.
6.022 x 10^22
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C.
1.2044 x 10^23
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D.
1.5055 x 10^23
Solution
Number of molecules = moles x Avogadro's number = 0.25 moles x 6.022 x 10^23 molecules/mole = 1.5055 x 10^23 molecules.
Correct Answer: B — 6.022 x 10^22
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Q. How many molecules are present in 2 moles of water (H2O)? (2022) 2022
-
A.
6.022 x 10^23
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B.
1.2044 x 10^24
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C.
3.011 x 10^23
-
D.
1.2044 x 10^23
Solution
Number of molecules = moles x Avogadro's number = 2 moles x 6.022 x 10^23 molecules/mole = 1.2044 x 10^24 molecules.
Correct Answer: B — 1.2044 x 10^24
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Q. How many moles are in 100 grams of NaOH? (2022)
-
A.
2.5
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B.
1.25
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C.
0.5
-
D.
3
Solution
Molar mass of NaOH = 23 + 16 + 1 = 40 g/mol. Number of moles = mass/molar mass = 100 g / 40 g/mol = 2.5 moles.
Correct Answer: B — 1.25
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Q. How many moles are in 32 grams of O2? (2021)
Solution
Molar mass of O2 = 16*2 = 32 g/mol. Number of moles = mass/molar mass = 32g/32g/mol = 1 mole.
Correct Answer: A — 1
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Q. How many moles of solute are present in 500 mL of a 0.2 M solution? (2021) 2021
-
A.
0.1 moles
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B.
0.5 moles
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C.
0.2 moles
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D.
0.25 moles
Solution
Moles = Molarity * Volume (L) = 0.2 M * 0.5 L = 0.1 moles.
Correct Answer: A — 0.1 moles
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Q. How many orbitals are present in the d-subshell? (2023)
Solution
The d-subshell has 5 orbitals.
Correct Answer: C — 5
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Q. How many orbitals are present in the p subshell? (2023)
Solution
The p subshell has 3 orbitals (px, py, pz).
Correct Answer: C — 3
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Q. How many ways can 2 boys and 3 girls be selected from 5 boys and 6 girls?
-
A.
100
-
B.
150
-
C.
200
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D.
250
Solution
The number of ways is 5C2 * 6C3 = 10 * 20 = 200.
Correct Answer: B — 150
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Q. How many ways can 2 students be selected from a group of 5? (2019)
Solution
The number of ways to select 2 students from 5 is given by 5C2 = 10.
Correct Answer: A — 10
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Q. How many ways can 3 books be selected from a shelf of 10 books? (2022)
-
A.
120
-
B.
210
-
C.
100
-
D.
30
Solution
The number of ways to select 3 books from 10 is given by 10C3 = 120.
Correct Answer: B — 210
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Q. How many ways can 3 boys and 2 girls be seated in a row?
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A.
30
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B.
60
-
C.
120
-
D.
180
Solution
The number of ways to arrange 5 people is 5! = 120.
Correct Answer: C — 120
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Q. How many ways can 3 out of 8 different colored balls be chosen? (2022)
Solution
The number of ways to choose 3 balls from 8 is given by 8C3 = 56.
Correct Answer: A — 56
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Q. How many ways can 3 prizes be awarded to 10 students if no student can win more than one prize?
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A.
720
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B.
1000
-
C.
1200
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D.
100
Solution
The number of ways to award 3 prizes is P(10, 3) = 720.
Correct Answer: A — 720
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Q. How many ways can 3 students be selected from a group of 10?
-
A.
120
-
B.
90
-
C.
100
-
D.
80
Solution
The number of ways to select 3 students from 10 is given by 10C3 = 120.
Correct Answer: A — 120
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Q. How many ways can 4 different fruits be selected from 8?
Solution
The number of ways to select 4 fruits from 8 is given by 8C4 = 70.
Correct Answer: B — 56
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Q. How many ways can 4 letters be chosen from the word 'COMBINATION'?
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A.
210
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B.
120
-
C.
150
-
D.
180
Solution
The number of ways to choose 4 letters from 11 is 11C4 = 330.
Correct Answer: A — 210
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Q. How many ways can 4 prizes be distributed among 10 students if each student can receive at most one prize? (2019)
-
A.
5040
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B.
720
-
C.
1000
-
D.
1200
Solution
The number of ways to distribute 4 prizes among 10 students is 10P4 = 5040.
Correct Answer: A — 5040
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Q. How many ways can 5 different letters be arranged if 2 letters are always together?
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A.
48
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B.
120
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C.
240
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D.
720
Solution
Treat the 2 letters as one unit. So, we have 4 units to arrange: 4! * 2! = 48.
Correct Answer: C — 240
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Q. How many ways can 5 different letters be arranged if 2 letters must always be together?
-
A.
60
-
B.
120
-
C.
240
-
D.
720
Solution
Treat the 2 letters as one unit. So, we have 4 units to arrange: 4! * 2! = 48.
Correct Answer: C — 240
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Q. How many ways can 6 different letters be arranged if 2 letters are always together?
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A.
120
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B.
240
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C.
720
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D.
1440
Solution
Treat the 2 letters as one unit. So, we have 5 units to arrange: 5! = 120. The 2 letters can be arranged in 2! = 2 ways. Total = 120 * 2 = 240.
Correct Answer: D — 1440
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Q. How many ways can 7 different books be arranged on a shelf if 3 specific books must be together?
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A.
720
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B.
120
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C.
5040
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D.
840
Solution
Treat the 3 specific books as one unit. So, we have 5 units to arrange: 5! * 3! = 360.
Correct Answer: C — 5040
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Q. How many ways can 8 different books be arranged on a shelf if 3 specific books must be together?
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A.
720
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B.
5040
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C.
40320
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D.
2880
Solution
Treat the 3 specific books as one unit. So, we have 6 units to arrange: 6! = 720. The 3 books can be arranged in 3! = 6 ways. Total = 720 * 6 = 4320.
Correct Answer: B — 5040
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Q. How many ways can 8 different colored balls be arranged in a line?
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A.
40320
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B.
720
-
C.
1000
-
D.
100
Solution
The number of arrangements is 8! = 40320.
Correct Answer: A — 40320
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Q. How many ways can a committee of 4 be formed from 10 people? (2019)
-
A.
210
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B.
120
-
C.
100
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D.
30
Solution
The number of ways to form a committee of 4 from 10 is given by 10C4 = 210.
Correct Answer: A — 210
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Q. How much heat is required to raise the temperature of 250 g of water from 25°C to 75°C? (Specific heat of water = 4.2 J/g°C) (2020)
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A.
5250 J
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B.
4200 J
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C.
2500 J
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D.
1000 J
Solution
Heat required = mass × specific heat × change in temperature = 250 g × 4.2 J/g°C × (75°C - 25°C) = 5250 J.
Correct Answer: A — 5250 J
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Q. How much heat is required to raise the temperature of 500 g of water from 25°C to 75°C? (2020)
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A.
10000 J
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B.
5000 J
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C.
20000 J
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D.
15000 J
Solution
Q = mcΔT = 500 g * 4.2 J/g°C * (75 - 25)°C = 10000 J.
Correct Answer: D — 15000 J
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Q. How much work is done when a force of 10 N moves an object 5 m in the direction of the force?
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A.
25 J
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B.
50 J
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C.
75 J
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D.
100 J
Solution
Work = Force * Distance = 10 N * 5 m = 50 J.
Correct Answer: B — 50 J
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Q. How much work is done when a force of 30 N moves an object 4 m in the direction of the force?
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A.
120 J
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B.
90 J
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C.
60 J
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D.
30 J
Solution
Work = Force * Distance = 30 N * 4 m = 120 J.
Correct Answer: A — 120 J
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Q. Identify the oxidizing agent in the reaction: 2H2 + O2 → 2H2O. (2023)
-
A.
H2
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B.
O2
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C.
H2O
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D.
None of the above
Solution
O2 is the oxidizing agent as it gains electrons and is reduced to H2O.
Correct Answer: B — O2
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Q. If 0.1 M acetic acid (CH3COOH) is 1% ionized, what is the concentration of H+ ions?
-
A.
0.001 M
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B.
0.01 M
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C.
0.1 M
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D.
0.2 M
Solution
Ionization = 1% of 0.1 M = 0.001 M, so [H+] = 0.001 M.
Correct Answer: B — 0.01 M
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