Question

here is a graph of the pressure of oxygen (o₂) in a reaction vessel during a certain chemical reaction. use this graph to answer the questions in the table below.
is o₂ being created or destroyed by the chemical reaction?
created
destroyed
neither created nor destroyed
if o₂ is being created or destroyed, what is the rate at which it is being created or destroyed 90 seconds after the reaction starts?
round your answer to 2 significant digits. also be sure your answer has the correct unit symbol.
if o₂ is being created or destroyed, what is the average rate at which it is being created or destroyed during the first 90 seconds of the reaction?
round your answer to 2 significant digits. also be sure your answer has the correct unit symbol.

Explanation:

Step1: Determine creation or destruction

As the pressure of $O_2$ is decreasing over time according to the graph, $O_2$ is being destroyed.

Step2: Find the instantaneous rate at 90 seconds

To find the instantaneous rate at 90 seconds, we need to find the slope of the tangent line to the curve at $t = 90$ s. This is a bit more complex for a non - linear graph. But we can estimate by considering a small interval around 90 s. Let's assume we take a small interval $\Delta t$ around 90 s. If we consider a very small interval (for simplicity, we can estimate visually). The pressure at $t = 90$ s is around 1.0 atm and if we consider a small interval say from $t=85$ s to $t = 95$ s. The pressure at $t = 85$ s is around 1.1 atm and at $t=95$ s is around 0.9 atm. The change in pressure $\Delta P=0.9 - 1.1=- 0.2$ atm and $\Delta t = 95 - 85 = 10$ s. The instantaneous rate $r=\frac{\Delta P}{\Delta t}=\frac{- 0.2}{10}=-0.020$ atm/s.

Step3: Find the average rate in the first 90 seconds

The initial pressure of $O_2$ at $t = 0$ s is $P_0=2.21$ atm and the pressure at $t = 90$ s is $P_{90}\approx1.0$ atm. The average rate $r_{avg}=\frac{\Delta P}{\Delta t}=\frac{P_{90}-P_0}{90 - 0}=\frac{1.0 - 2.21}{90}=\frac{-1.21}{90}\approx - 0.013$ atm/s.

Answer:

Is $O_2$ being created or destroyed by the chemical reaction? Destroyed
If $O_2$ is being created or destroyed, what is the rate at which it is being created or destroyed 90 seconds after the reaction starts? $-0.020$ atm/s
If $O_2$ is being created or destroyed, what is the average rate at which it is being created or destroyed during the first 90 seconds of the reaction? $-0.013$ atm/s