## Basic Chemical Engineering Questions and Answers Part-1

1. How many grams of NaCl represent 1 mole?
a) 23
b) 35.5
c) 58.5
d) 69.5

Answer: c
Explanation: Molecular weight of NaCl is 58.5 grams, => 1 mole represent 58.5 grams of NaCl.

2. How many atoms of carbon represent 1.5 mole?
a) 6.022 X 1023
b) 1.2044 X 1023
c) 3.011 X 1023
d) 9.033 X 1023

Answer: d
Explanation: Number of moles = number of atoms/Avogadro’s number, => 1.5 = n/6.022 X 1023, => n = 9.033 X 1023.

3. Calculate the number of moles in 42 grams of NaHCO3?
a) 0.5
b) 1
c) 1.5
d) 2

Answer: a
Explanation: Molecular weight of NaHCO3 = 84 grams, => number of moles = 42/84 = 0.5.

4. Calculate the number of moles in 369 grams of CaOCl2?
a) 1
b) 2
c) 3
d) 4

Answer: c
Explanation: Molecular weight of CaOCl2 = 127, => number of moles = 369/127 = 3.

5. Which of the following has the same number of moles as in 398 grams of CuSO4?
a) 2 grams of hydrogen
b) 40 grams of oxygen
c) 35 grams of nitrogen
d) 58.5 grams of Sodium chloride

Answer: b
Explanation: Number of moles of CuSO4 = 398/ 159 ≈ 2.5, and number of moles of oxygen = 40/16 = 2.5.

6. What are the number of atoms of chlorine in 250.5 grams of Cl2O6?
a) 1.806 X 1024
b) 2.408 X 1024
c) 9.033 X 1023
d) 6.022 X 1023

Answer: a
Explanation: Number of moles of Cl2O6 = 250.5/167 = 1.5, => number of atoms of chlorine = 2*1.5*(6.022 X 1023) = 1.806 X 1024.

7. What are the number of moles of Hydrogen in 158 grams of Ammonium Bicarbonate?
a) 5
b) 10
c) 15
d) 20

Answer: b
Explanation: Molecular Weight of ammonium bicarbonate (NH4HCO3) = 79 grams, => moles = 158/79 = 2, => Number of moles of hydrogen = 2* 5 = 10.

8. What are the number of moles of nitrogen in 274 grams of (NH4)2Ce(NO3)6?
a) 16
b) 8
c) 6
d) 4

Answer: d
Explanation: Molecular Weight of (NH4)2Ce(NO3)6 = 548 grams, => moles of (NH4)2Ce(NO3)6 = 274/548 = 0.5, => number of moles of nitrogen = 0.5*8 = 4.

9. What are the number of moles of hydrogen in NH4[Cr(SCN)4(NH3)2] if the weight of nitrogen in it is 49 grams?
a) 3.5
b) 5
c) 7
d) 10

Answer: b
Explanation: Moles of nitrogen = 49/14 = 3.5, => moles of NH4[Cr(SCN)4(NH3)2] = 3.5/7 = 0.5, => moles of hydrogen = 0.5*10 = 5.

10. What are the number of molecules of water in CuSO4•5H2O, if the weight of oxygen in it is 36 grams?
a) 3.25 X 1023
b) 5.25 X 1023
c) 7.52 X 1023
d) 9.52 X 1023

Answer: c
Explanation: Number of moles of oxygen = 36/16 =2.25, => number of moles of CuSO4•5H2O = 2.25/9 = 0.25, => number of molecules of water = 0.25*5*(6.022 X 1023) = 7.52 X 1023.