*The decomposition of acetaldehyde is a first order reaction with a specific rate constant of 6.0 X 10^-1 / min.

CH₃CHO --> CH₄ + CO

1. Calculate the initial rate when the concentration of acetaldehyde is 0.80M.

2. Calculate the time needed for the concentration of the acetaldehyde to decrease by 0.05 M from an initial concentration of 1.20 M.

40

To calculate the initial rate when the concentration of acetaldehyde is 0.80M, we'll need to use the rate law for a first-order reaction:

Rate = k[A]

Where:
Rate = initial rate (mol/L/min)
k = rate constant (min^(-1))
[A] = concentration of acetaldehyde (M)

1. Calculate the initial rate:
Given:
[A] = 0.80 M
k = 6.0 × 10^(-1) min^(-1)

Substituting the given values into the rate law equation:

Rate = (6.0 × 10^(-1) min^(-1)) × (0.80 M)
Rate = 4.8 × 10^(-1) M/min

Therefore, the initial rate when the concentration of acetaldehyde is 0.80 M is 0.48 M/min.

To calculate the time needed for the concentration of acetaldehyde to decrease by 0.05 M from an initial concentration of 1.20 M, we can use the first-order reaction integrated rate law:

ln([A]t/[A]0) = -kt

Where:
[A]t = concentration of acetaldehyde at time t (M)
[A]0 = initial concentration of acetaldehyde (M)
k = rate constant (min^(-1))
t = time (min)

2. Calculate the time needed:
Given:
[A]t = [A]0 - 0.05 M = 1.20 M - 0.05 M = 1.15 M
[A]0 = 1.20 M
k = 6.0 × 10^(-1) min^(-1)

Substituting the given values into the integrated rate law equation:

ln(1.15/1.20) = -(6.0 × 10^(-1) min^(-1)) × t

Simplifying:

ln(0.9583) = -(6.0 × 10^(-1) min^(-1)) × t

Using logarithmic properties to solve for t:

t = ln(0.9583) / (-6.0 × 10^(-1) min^(-1))

Calculating this value:

t ≈ 0.043 min

Therefore, the time needed for the concentration of acetaldehyde to decrease by 0.05 M from an initial concentration of 1.20 M is approximately 0.043 min.

To calculate the initial rate of the reaction (question 1), you would need to use the specific rate constant and the initial concentration of acetaldehyde. The rate equation for a first-order reaction is given by:

Rate = k[A]

Where:
Rate = Initial rate of reaction
k = Specific rate constant
[A] = Concentration of the reactant (in this case, acetaldehyde)

1. Calculate the initial rate when the concentration of acetaldehyde is 0.80 M:

Rate = k[A]

Plugging in the values given:
Rate = (6.0 x 10^-1 / min) x (0.80 M)
Rate = 4.8 x 10^-1 min^-1

Therefore, the initial rate is 0.48 min^-1.

Now, let's move on to question 2 to calculate the time needed for the concentration of acetaldehyde to decrease by 0.05 M from an initial concentration of 1.20 M.

For a first-order reaction, the integrated rate equation is given as:

ln([A]t / [A]0) = -kt

Where:
[A]t = Concentration of acetaldehyde at time t
[A]0 = Initial concentration of acetaldehyde
k = Specific rate constant
t = Time

Rearranging the equation, we get:

t = - (ln([A]t / [A]0)) / k

Plugging in the values given:
t = - (ln(1.15 / 1.20)) / (6.0 x 10^-1 / min)
t ≈ 0.0803 min

Therefore, the time needed for the concentration of acetaldehyde to decrease by 0.05 M from an initial concentration of 1.20 M is approximately 0.0803 minutes.