What does rate of reaction measure?
How fast a reaction goes - how quickly reactants are used up (or products made) per unit time. On a concentration-time graph it is the steepness of the curve.
// chemistry › Reaction Rate
Rate of Reaction
Calculate reaction rate = −Δ[R]/Δt: how fast a reactant is used up, with symbol legend and real-world examples.
\text{Rate} = \frac{-Δ[R]}{Δ t}
Frequently asked questions
Why the minus sign?
Because the reactant is being used up, so its change is negative. The minus flips it to a positive rate. If you track a product instead (which grows), no minus is needed.
Where does it matter day to day?
Food spoiling, medicine shelf life, fuel burning in an engine, cement setting, glow sticks. Anywhere a reaction needs to be sped up or slowed down in time.
Why does the rate usually slow over time?
Reactions need collisions, and as reactants run out there are fewer to collide, so the rate drops - the curve is steep at first and flattens later.
How do you speed a reaction up?
Heat it, increase concentration or pressure, increase a solid's surface area, or add a catalyst. All make successful collisions more frequent or easier.