Question

How can the rate of reaction be calculated from a graph?

Answer 1

You compute the rate of reaction from the slope of a graph of concentration versus time.
Expect we have a reaction $2A$ →$3B$.
By definition, rate = $\dfrac{{ - 1{{\Delta }}\left[ {{A}} \right]}}{{{{\Delta t}}}}$ =$\dfrac{{ + 1{{\Delta }}\left[ {{B}} \right]}}{{3{{\Delta t}}}}$ .
On the off chance that you plot a diagram of [A] versus t and draw a line tangent to the graph, at that point rate = $\raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} {{ }} \times {{ }}\left| {slope} \right|$ of the line (rate is consistently a positive number).

Complete step by step answer:
1)To locate the instantaneous rate of reaction at a given time:
2)Assume that each tick on the time pivot represents $10{{ }}s$. Mark a point on the graph that corresponds to a given time (say,$40{{ }}s$).
3)Draw a straight line (green) tangent to the curve by then.
4)Pick two convenient focuses on the tangent line, for instance, where it crosses the horizontal and vertical axes (I assume the concentration has units of g/L).
6)Note the coordinates of these points, say ($0{{ }}s,{{ }}50{{ }}g/L$ ) and ($52{{ }}s,{{ }}0{{ }}g/L$ ).
7)Compute the adjustment in concentration.
$\Delta {{ }}\left[ {{{ }}A{{ }}} \right]{{ }} = \left[ {{{ }}A{{ }}_2{{ }}} \right]{{ }}-{{ }}\left[ {{{ }}A{{ }}_1{{ }}} \right]{{ }} = {{ }}\left( {0.0{{ }}-{{ }}50.0} \right){{ }}g/L{{ }} = {{ }} - {{ }}50.0{{ }}g/L$
1)Calculate the change in time
$\Delta {{ }}t{{ }} = {{ }}t{{ }}_2{{ }}-{{ }}t{{ }}_1{{ }} = {{ }}\left( {82{{ }}-{{ }}0} \right){{ }}s{{ }} = {{ }}82{{ }}s$
2)Calculate the slope.
Slope =$\dfrac{{{{\Delta }}\left[ {{A}} \right]}}{{{{\Delta t}}}}$ =$\dfrac{{\left[ {{{A}}_2\left] - \right[{{A}}_1} \right]}}{{{{t}}_2-{{t}}_1}}$ = =
3)Calculate the rate.

Note:
1)Reaction rate is calculated utilizing the equation rate =$\Delta \left[ C \right]/\Delta t$ , where $\Delta \left[ C \right]$ is the change in product concentration during the time period $\delta t$ .
2)The rate of reaction can be seen by viewing the disappearance of a reactant or the presence of a product over a long time.
3)On the off chance that a reaction produces a gas, for example, oxygen or carbon dioxide, there are two different ways to measure the reaction rate: using a gas needle to gauge the gas produced, or calculating the reduction in the mass of the reaction solution.