1. There were 10 moles of a substance present initially in a system, 5 moles were added to it and a reaction occurred so that its moles are reduced by 20%, what are the final moles of a substance in the system?
a) 10
b) 12
c) 15
d) 18
Explanation: Final moles of substance = (10 + 5)*80/100 = 12.
2. There were 15 moles of a substance present initially in a system, 25 moles were added to it and a reaction occurred so that its moles are reduced by 50%, what are the final moles of a substance in the system?
a) 10
b) 15
c) 20
d) 40
Explanation: Final moles of substance = (15 + 25)*50/100 = 20.
3. 10 moles of A were present in a system initially, and 12 moles of C are added to it, it undergoes the reaction 2A + 3C -> 2B, what are number of moles of B produced?
a) 4
b) 5
c) 8
d) 12
Explanation: Moles of B = 2*4 = 8.
4. 10 moles of A were present in a system initially, and 8 moles of C are added to it, it undergoes the reaction 5A + 3C -> 4B, what are number of moles of B produced?
a) 4
b) 6
c) 8
d) 10
Explanation: Moles of B = 4*2 = 8.
5. 8 moles of A were present in a system initially, and 24 moles of B are added to it, it undergoes the reaction 2A + 3B -> 4C + 5D, what are the number of moles of D produced?
a) 10
b) 20
c) 30
d) 40
Explanation: Moles of D = 5*4 = 20.
6. Which of the following is constant in a closed system?
a) Energy
b) Mass
c) Temperature
d) Momentum
Explanation: A material neither leaves nor enters a closed system.
7. How is the boundary wall of a closed system?
a) Impermeable
b) Permeable
c) Rigid
d) None of the mentioned
Explanation: Since the matter is not allowed to cross the boundary wall of a closed system, so the wall is impermeable.
8. Desert Cooler is an example of which of the following?
a) Closed System
b) Open System
c) Isolated System
d) None of the mentioned
Explanation: Since water is filled and then it vaporizes in desert cooler, this means the material is flowing in and out of the system, so it is an open system.
9. A jar filled with water is an example of which of the following?
a) Closed System
b) Open System
c) Isolated System
d) None of the mentioned
Explanation: Since water is neither leaving nor entering the jar, this means it is a closed system.
10. A pressure cooker is an example of which of the following?
a) Closed System
b) Open System
c) Isolated System
d) None of the mentioned
Explanation: Since steam is expelled outside in the cooker as the temperature increase, it is an open system