Use a copy of the Periodic Table where you need one.
Marble chips react with excess dilute hydrochloric acid. Why does the graph of volume of gas against time level off?
Source: Learners' Alley, Rate of Reactions slides
Which change does not increase the rate of reaction between marble chips and dilute hydrochloric acid?
Source: Learners' Alley, Rate of Reactions slides
Answer these questions about rates of reaction.
Source: Learners' Alley, Rate of Reactions slides
For which reaction is pressure least likely to affect the speed of reaction?
Source: 2024 AMKSS Prelim P1 Q31
Potassium chlorate decomposes when heated: 2KClO3(s) → 2KCl(s) + 3O2(g). Manganese(IV) oxide is a catalyst. In experiment 1, powdered manganese(IV) oxide is heated with 0.1 g of powdered potassium chlorate. In experiment 2, lumps of manganese(IV) oxide are heated with 0.2 g of powdered potassium chlorate. What are the initial rate and the final volume of oxygen in experiment 2, compared with experiment 1?
| initial rate of reaction | final volume of oxygen formed | |
|---|---|---|
| A | faster than experiment 1 | larger than experiment 1 |
| B | faster than experiment 1 | same as experiment 1 |
| C | slower than experiment 1 | larger than experiment 1 |
| D | slower than experiment 1 | same as experiment 1 |
Source: 2024 SJI Prelim P1 Q31
Aqueous hydrogen peroxide decomposes at room temperature to form water and oxygen. It decomposes faster when it is warmed and kept at 50 °C.
Source: AES Prelim P2 A2(c)
Catalysts are used to speed up many reactions.
Source: 2024 QTSS Prelim P2 A9(a)
BThe marble chips have all reacted.[1]
The acid is in excess, so the marble chips are the limiting reactant. When they are used up, no more gas forms.
Cusing a larger volume of the same acid[1]
More acid of the same concentration has the same number of particles per unit volume, so the frequency of effective collisions is unchanged.
The volume of gas given off and the mass of the reaction mixture. [1]
A collision with energy greater than or equal to the activation energy, which leads to a reaction. [1]
A substance that increases the rate of a reaction without being chemically changed at the end of the reaction. [1]
Particles have more kinetic energy and collide more often, and more of them have energy greater than or equal to the activation energy. [1]
So the frequency of effective collisions increases. [1]
C2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)[1]
Pressure affects the rate only when a reactant is a gas. In C, the reactants are a solid and a liquid.
Cslower, and a larger volume[1]
Lumps of catalyst have a smaller surface area, so the rate is slower. Twice the mass of potassium chlorate gives twice the volume of oxygen.
When warmed, the particles gain energy and move faster, and more particles have energy greater than or equal to the activation energy. [1]
This leads to a higher frequency of effective collisions between the reacting molecules. [1]
A catalyst provides an alternative pathway with a lower activation energy for the reaction. [1]
This leads to a higher frequency of effective collisions between the particles, so the rate of reaction is higher. [1]