Calculating Rates of ReactionsOxford AQA IGCSE Chemistry: Flashcards

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Define rate of reaction.

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Define rate of reaction.: A measure of how quickly a reactant is used up or a product is formed in a chemical reaction.
State the equation for rate of reaction using amount of reactant used.: Rate = amount of reactant used ÷ time.
State the equation for rate of reaction using amount of product formed.: Rate = amount of product formed ÷ time.
Give three possible units for the 'amount' in a rate of reaction calculation.: Grams (mass), cm³ (volume of gas), or mol/dm³ (concentration).
If 30 cm³ of gas forms in 15 seconds, what is the mean rate of reaction?: 30 ÷ 15 = 2 cm³/s.
On a graph of product formed against time, what does a steeper gradient mean?: A faster rate of reaction.
Why does the gradient of a rate–time graph decrease as the reaction proceeds?: Because reactants are being used up, so there are fewer particles able to react and collide.
What does a flat (horizontal) section of a reaction-progress graph indicate?: The reaction has finished, so no more product is being formed.
How do you find the mean rate of reaction from a graph?: Draw a straight line between two points and calculate its gradient (change in y ÷ change in x).
How do you find the rate of reaction at one specific instant from a curved graph?: Draw a tangent to the curve at that point and calculate the gradient of the tangent.
What is plotted on the axes of a typical rate-of-reaction graph?: Amount of product formed (or reactant used up) on the y-axis, time on the x-axis.
What time unit is usually used when calculating rate of reaction?: Seconds.