| 2041 |
What is the overall reaction in a hydrogen–oxygen fuel cell? |
Chemistry
Batteries, fuel cells and corrosion |
Easy |
| 2042 |
Why does a mercury cell give a nearly constant voltage throughout its life? |
Chemistry
Batteries, fuel cells and corrosion |
Medium |
| 2043 |
During discharge of a lead storage battery, what is formed at both electrodes? |
Chemistry
Batteries, fuel cells and corrosion |
Medium |
| 2044 |
A scratched galvanised iron sheet still does not rust easily. What is the best explanation? |
Chemistry
Batteries, fuel cells and corrosion |
Hard |
| 2045 |
What are the usual units of the rate of a reaction in solution? |
Chemistry
Rate of reaction |
Easy |
| 2046 |
How is the instantaneous rate of a reaction found from a graph of reactant concentration against time? |
Chemistry
Rate of reaction |
Easy |
| 2047 |
In 2N₂O₅ → 4NO₂ + O₂, N₂O₅ disappears at 0.02 mol L⁻¹ s⁻¹. At what rate is NO₂ formed? |
Chemistry
Rate of reaction |
Medium |
| 2048 |
For 2HI(g) → H₂(g) + I₂(g), which expression correctly gives the rate of reaction? |
Chemistry
Rate of reaction |
Medium |
| 2049 |
Why does powdered marble react faster with dilute HCl than a single lump of the same mass? |
Chemistry
Rate of reaction |
Hard |
| 2050 |
Which statement about molecularity is correct? |
Chemistry
Rate law, order and molecularity |
Easy |
| 2051 |
The rate constant of a reaction has units of s⁻¹. What is the order of the reaction? |
Chemistry
Rate law, order and molecularity |
Easy |
| 2052 |
For 2NO + O₂ → 2NO₂, rate = k[NO]²[O₂]. By what factor does the rate change if [NO] is doubled while [O₂] is … |
Chemistry
Rate law, order and molecularity |
Medium |
| 2053 |
For a reaction A + B → products, doubling [A] alone doubles the rate, while doubling [B] alone has no effect … |
Chemistry
Rate law, order and molecularity |
Medium |
| 2054 |
For CHCl₃ + Cl₂ → CCl₄ + HCl, rate = k[CHCl₃][Cl₂]^½. What are the units of k? |
Chemistry
Rate law, order and molecularity |
Hard |
| 2055 |
The half-life of a first-order reaction is 10 minutes. What is its rate constant? |
Chemistry
Integrated rate equations |
Easy |
| 2056 |
For which order of reaction is the half-life independent of the initial concentration? |
Chemistry
Integrated rate equations |
Easy |
| 2057 |
How many half-lives are needed for 75% of a first-order reaction to be completed? |
Chemistry
Integrated rate equations |
Medium |
| 2058 |
A zero-order reaction has [R]₀ = 0.2 mol L⁻¹ and k = 0.01 mol L⁻¹ s⁻¹. What is its half-life? |
Chemistry
Integrated rate equations |
Medium |
| 2059 |
The acid-catalysed hydrolysis of ethyl acetate behaves as a first-order reaction even though it involves este… |
Chemistry
Integrated rate equations |
Hard |
| 2060 |
How does a catalyst increase the rate of a reaction? |
Chemistry
Temperature and rate |
Easy |