General Chemistry Ii - Midterm 1 Answ
ersStudent name: ________________________________
Student ID Number: ________________________________
Length: 1.5 hours
Instructor: Sandra Warren
Instructions: Please use pen. Calculators allowed.
Part A: (3 marks each) Q. 1 | Q.2 | Q.3 | Q.4 | Q.5 | Q.6 |
Part B: (10 marks each) Q.1 | Q.2 | Q.3 | Q4. |
Total: / 52 marks
Part A: Short Answer. Only answer 4 of the 6 questions.
(3 marks each)
A1. Under standard state conditions, predict which has the larger standard entropy and give a reason why: 1 mole each of NO and NO2 ? ANS: Both NO and NO2 are gases under standard conditions. Each molecule of NO2 has three atoms, and each molecule of NO has two atoms. Thus, NO2 should have the larger standard molar entropy than NO. Molecules with many atoms has more variations in how it can vibrate than a molecule with fewer atoms. This means more ways to distribute energy- or greater energy dispersal at any given temperature and larger entropy.
A2. ΔGo for reaction A is -50 kJ mol-1. ΔGo for reaction B is -75 kJ mol-1. Which reaction is faster? How do you know? Nothing can be said about the rates of these two reactions. G is a state function and does not depend on the reaction rate.
A3. Why are condensed phases such as solids and pure liquids not included in an expression for an equilibrium constant?
The concentrations of these species do not change as they are used up or created in a reaction – both the quantity and the volume change, but concentration is the quotient of the two, which does not change.
A4. In a reaction mechanism, what is the difference between a reaction intermediate and a catalyst? Define the term “rate limiting step.” An intermediate is produced in an early step and consumed in a later step. A catalyst is consumed in an early step and reproduced in a later step.
The rate limiting step is the slowest step in the mechanism of a multistep reaction.
A5. Which direction
Student ID Number: ________________________________
Length: 1.5 hours
Instructor: Sandra Warren
Instructions: Please use pen. Calculators allowed.
Part A: (3 marks each) Q. 1 | Q.2 | Q.3 | Q.4 | Q.5 | Q.6 |
Part B: (10 marks each) Q.1 | Q.2 | Q.3 | Q4. |
Total: / 52 marks
Part A: Short Answer. Only answer 4 of the 6 questions.
(3 marks each)
A1. Under standard state conditions, predict which has the larger standard entropy and give a reason why: 1 mole each of NO and NO2 ? ANS: Both NO and NO2 are gases under standard conditions. Each molecule of NO2 has three atoms, and each molecule of NO has two atoms. Thus, NO2 should have the larger standard molar entropy than NO. Molecules with many atoms has more variations in how it can vibrate than a molecule with fewer atoms. This means more ways to distribute energy- or greater energy dispersal at any given temperature and larger entropy.
A2. ΔGo for reaction A is -50 kJ mol-1. ΔGo for reaction B is -75 kJ mol-1. Which reaction is faster? How do you know? Nothing can be said about the rates of these two reactions. G is a state function and does not depend on the reaction rate.
A3. Why are condensed phases such as solids and pure liquids not included in an expression for an equilibrium constant?
The concentrations of these species do not change as they are used up or created in a reaction – both the quantity and the volume change, but concentration is the quotient of the two, which does not change.
A4. In a reaction mechanism, what is the difference between a reaction intermediate and a catalyst? Define the term “rate limiting step.” An intermediate is produced in an early step and consumed in a later step. A catalyst is consumed in an early step and reproduced in a later step.
The rate limiting step is the slowest step in the mechanism of a multistep reaction.
A5. Which direction