Unit 1 - Rates of Reaction
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What is meant by the rate of a chemical reaction?
The rate of a chemical reaction is a measure of how fast the reactants are being used up and how fast the products are being made.
Name the four factors which speed up the rate of a reaction.
Increase temperature Increase concentration of a reactant Increase the surface area (decrease particle size) Use a suitable catalyst
What word is used to describe a biological catalyst?
Enzyme
The rate can be determined by measuring what quantities?
changes in the mass of the reactants or products changes in the volume of the reactants or products changes in the concentration of the reactants or products
When dilute hydrochloric acid reacts with magnesium metal, magnesium chloride and hydrogen gas are produced. Describe a method to measure the rate of this reaction in the lab.
-A balance can be used to measure the mass of the apparatus throughout the reaction. As hydrogen bubbles escape, the apparatus will lose mass. -The volume of gas could be collected in a gas syringe or over water (as long as it is insoluble in water).
How is the average rate of reaction calculated?
Average rate = Change in measurable quantity ÷ change in time Average rate = ∆ Quantity ÷ ∆ Time
The unit that rate is measured in depends on the measured quantity. State the units used when: a change in mass is measured in grams and a change in time in seconds a change in concentration is measured (in mol l-1) and a change in time in minutes a change in volume measured in cubic centimetres and a change in time in seconds
a change in mass is measured in grams and a change in time in seconds = grams per second ( g s-1 or g / s ) a change in concentration is measured ( in mol l-1 ) and a change in time in minutes = moles per litre per minute ( mol l-1 min-1 or mol l-1 / min) a change in volume measured in cubic centimetres and a change in time in seconds = cm3 per second ( cm3 s -1 or cm3 / s )
If a reaction produced 120cm3 of gas in 15 seconds, what is the average rate of reaction?
Average rate = ∆ Quantity ÷ ∆ Time = 120 ÷ 15 = 8 cm3 s-1
Explain what happens to the rate of reaction as the reaction progresses?
As the reaction progresses the rate of reaction decreases. This is because as reactants are used up, there will be fewer collisions and the reaction slows down.
What name is given to the point on a rate curve where it levels off and no longer increases.
End Point or Reaction End Point