The following reaction is observed in a lab experiment: #A + 2B -> C + D# In this experiment, it required 750 s for the concentration of #C# to change from 0.333 M to 0.750 M. What is the rate of the reaction?
The rate of a reaction is simply a measure of how the concentration of the reactants or the concentration of the products changes over time.
In order to express the rate of a reaction, you must essentially figure out the change that takes place in the concentration of the reactants or of the products per unit of time.
Usually, this unit of time is the second,
Your chemical reaction looks like this
#"A" + 2"B" -> "C" + "D"#
If you take
#color(blue)(|bar(ul(color(white)(a/a)"rate" = (Delta["C"])/(Deltat)color(white)(a/a)|)))#
In your case, you know that the concentration of
#Delta["C"] = "0.750 M" - "0.333 M"#
#Delta["C"] = "0.417 M"#
The rate of the reaction will thus be
#"rate" = "0.417 M"/"750 s" = color(green)(|bar(ul(color(white)(a/a)5.6 * 10^(-4)"M s"^(-1)color(white)(a/a)|)))#
The answer is rounded to two sig figs.
This tells you that as the reaction proceeds, the concentration of