Using the following data table and graph, calculate the average k from the data. amount co2 (ml) amount of white solid (g) y x 10 0.15 20 0.30 30 0.46 40 0.62 50 0.77 k =

k = 63 mL/g

The equation for the straight line has the form

V = km +b

The formula for the slope k is  

k = ΔV/Δm = (V₂ -V₁)/(m₂ - m₁)

So, we pick any two points on the line, preferably as far apart as possible.

I will choose the points (0.77, 50) and (0.10, 8). Then

k = (50 mL – 8 mL)/(0.77 g – 0.10 g) = 42 mL/0.67 g = 63 mL/g

In other words, you get 63 mLCO₂ for every 1 g CaCO₃.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.