# Given the following graph for a reactant concentration as a function of time, estimate the instantaneous rate of reaction at #"40 s"#?

##### 1 Answer

The **instantaneous rate of reaction** at a specific time is given by *the line tangent to the curve* that describes the slope at that specific time.

You are already given the tangent line, so what you can do is choose the easiest points to consider when calculating the slope at

You will have to stare at the graph and estimate

However, given that a **forward** reaction has a **positive** rate, take care to enter the ** magnitude**, instead of the value itself.

#color(blue)(|(Delta[A])/(Deltat)|) = |("0.48 M" - "0.24 M")/("0 s" - "70 s")|#

#= color(blue)(color(red)(bb(+))3.4_(29) xx 10^(-3))# #color(blue)("M/s")# where subscripts indicate digits past the last significant figure.

Note that if this is not correct, it is either a matter of estimation error (which is why I suggested to choose the points right at the grid intersections!) or the sign.