The rate and extent of chemical change

A reaction produces $72\,\text{cm}^3$ of gas in $40\,\text{s}$. Calculate its mean rate.

The mass of a reaction flask falls from $83.40\,\text{g}$ to $82.56\,\text{g}$ during the first $35\,\text{s}$. Calculate the mean rate of mass loss.

Reaction R forms $84\,\text{cm}^3$ of gas in $70\,\text{s}$. Reaction S forms $99\,\text{cm}^3$ in $55\,\text{s}$. Calculate both mean rates and determine the percentage by which S is faster than R.

A solid reactant is crushed into smaller pieces without changing its mass. State the effect on the reaction rate.

A student investigates how acid concentration affects the rate of gas production from marble chips. Describe how the student should collect suitable results while changing only the acid concentration.

In a turbidity experiment, relative acid concentrations of $20\%$, $40\%$ and $60\%$ give disappearance times of $162$, $81$ and $54\,\text{s}$. Describe the relationship shown and give two limitations of using the disappearance time as a rate measurement.

State the two conditions needed for a collision between reactant particles to lead to a reaction.

Explain, using collision theory, why increasing the pressure of two reacting gases increases their reaction rate at constant temperature.

A fixed $64\,\text{cm}^3$ of solid is cut either into cubes of side $2.0\,\text{cm}$ or cubes of side $1.0\,\text{cm}$. Calculate the total surface area for each set and explain which reacts faster with an acid.

Complete the statement: a catalyst increases reaction rate by providing a different pathway with a lower what?

An uncatalysed reaction has an activation energy of $79\,\text{kJ mol}^{-1}$ and an overall energy change of $-24\,\text{kJ mol}^{-1}$. A catalyst lowers the activation energy to $43\,\text{kJ mol}^{-1}$. State the reduction in activation energy and the catalysed reaction's overall energy change.

In the first $30\,\text{s}$, a reaction forms $48\,\text{cm}^3$ of gas with solid X and $21\,\text{cm}^3$ without X. Both tests eventually form $72\,\text{cm}^3$, and the dry mass of X is unchanged. Use the data to explain why X is a catalyst.

State what is meant by a reversible reaction.

The reaction $\mathrm{J+K\rightleftharpoons L+M}$ is reversible. State which substances react in the reverse reaction and which substances they form.

Blue hydrated copper sulfate is heated and forms white anhydrous copper sulfate and water. Adding water to the white solid reforms the blue substance. Explain how these observations show a reversible reaction and identify the change of condition used in each direction.

The forward direction of a reversible reaction is exothermic. State the energy-change type of the reverse direction.

The forward direction of a reversible reaction transfers $67\,\text{kJ mol}^{-1}$ to the surroundings. State the energy change for the reverse direction, including its sign.

A reversible reaction has a forward activation energy of $145\,\text{kJ mol}^{-1}$ and a forward overall energy change of $-38\,\text{kJ mol}^{-1}$. Calculate the reverse activation energy and state the reverse overall energy change.

State the relationship between the forward and reverse reaction rates at equilibrium.

A student says, 'The concentrations stay constant at equilibrium because both reactions have stopped.' Explain why this statement is incorrect.

In a sealed vessel, the measured forward and reverse rates in arbitrary units are: at $0\,\text{s}$, $5.2$ and $0.0$; at $20\,\text{s}$, $3.6$ and $1.7$; at $40\,\text{s}$, $2.8$ and $2.8$; at $60\,\text{s}$, $2.8$ and $2.8$. Determine when equilibrium is first reached and explain what the later readings show.

State Le Chatelier's principle for a system at equilibrium when a condition is changed.

For $\mathrm{R\rightleftharpoons2P}$ at equilibrium, some P is removed. Predict the direction of shift and explain it using Le Chatelier's principle.

The forward reaction $\mathrm{A+2B\rightleftharpoons C}$ is exothermic. At equilibrium, the concentration of B and the temperature are both increased. Explain why the information given is insufficient to predict the final change in the amount of C.

A reactant is added to a mixture at equilibrium. State the direction in which the equilibrium shifts.

For $\mathrm{D+E\rightleftharpoons F}$, some F is continuously removed from an equilibrium mixture. Explain the effect on the relative amount of F that is formed.

For $\mathrm{N_2+3H_2\rightleftharpoons2NH_3}$ at equilibrium, extra hydrogen is added while the temperature is kept constant. Predict the effect of this concentration change on the amounts of all three substances as a new equilibrium is reached.

The forward reaction is endothermic. State the effect of increasing temperature on the relative amount of products at equilibrium.

The forward direction of $\mathrm{X\rightleftharpoons Y}$ is exothermic. Explain the effect of decreasing temperature on the equilibrium yield of Y.

For the same equilibrium, product yields are $68\%$ at $300\,\text{K}$, $49\%$ at $400\,\text{K}$ and $32\%$ at $500\,\text{K}$. Reaction time falls as temperature rises. Deduce the energy-change type of the forward reaction and explain why an industrial process might use an intermediate temperature.

A gaseous equilibrium has three gas molecules on the left of its equation and one on the right. State the direction of shift when pressure is increased.

For $\mathrm{N_2(g)+3H_2(g)\rightleftharpoons2NH_3(g)}$, predict and explain the effect of increasing pressure on the equilibrium yield of ammonia.

Pressure is decreased for each equilibrium: (1) $\mathrm{2SO_2(g)+O_2(g)\rightleftharpoons2SO_3(g)}$; (2) $\mathrm{H_2(g)+I_2(g)\rightleftharpoons2HI(g)}$. Predict the effect on the product amount in each case and justify both predictions.