1. Chemical reactions may occur when two different molecules collide. The frequency and energy of the collisions determine how many reactions occur. How would you expect that frequency of collisions in a gas to change if the temperature changes from 293 K to 303 K (20°C to 30°C)?
A) 0% increase
B) 2% increase
C) 20% increase
D) 100% increase
2. What increase in reaction rate would you expect between two gaseous chemicals if the total pressure in the reaction vessel is doubled?
A) no change
B) double
C) quadruple
1. Isn't there a rule somewhere in kinetics that says something about "doubling the rate of reaction for every 10 degrees change in T?" So what percent would that be?
2. I don't like any of the choices. Doubling the pressure is the same as doubling the concentration and that will increase the rate of reaction. A is out. B is the best choice but the exact rate change depends upon the order of the reaction and/or on the kind of reaction; i.e., a reaction between the same particles or a reaction between different particles. Check my thinking.
To answer both of these questions, we need to consider the relationship between temperature, pressure, and the frequency of collisions in a gas.
1. The frequency of collisions in a gas is directly proportional to the temperature. As the temperature increases, the kinetic energy of the gas molecules increases, leading to more frequent and energetic collisions. Therefore, if the temperature changes from 293 K to 303 K, we can expect an increase in the frequency of collisions.
To calculate the percentage change in frequency, we need to find the difference between the two temperatures and divide it by the initial temperature (293 K) and then multiply by 100.
Percentage change in frequency = ((final temperature - initial temperature) / initial temperature) * 100
Using the given information, let's calculate the percentage change:
((303 K - 293 K) / 293 K) * 100 = (10 K / 293 K) * 100 ≈ 3.42%
Since none of the answer options match exactly, we can choose the answer option that is closest to the calculated value, which is approximately 3.42%. Therefore, the expected increase in the frequency of collisions would be approximately a 3% increase.
Answer: B) 2% increase
2. The increase in reaction rate between two gaseous chemicals is also influenced by the total pressure in the reaction vessel. According to the kinetic molecular theory, increasing the pressure of a gas leads to an increase in the frequency of collisions between gas molecules. Therefore, if the total pressure in the reaction vessel is doubled, we can expect an increase in the frequency of collisions.
Since the reaction rate is directly proportional to the frequency of collisions, if the frequency of collisions doubles, the reaction rate will also double.
Answer: B) double