Free Rate of Reaction MCQs with Answers

• A. concentration of a reactant or product per unit time
• B. temperature of the mixture per unit time
• C. mass of the catalyst per unit time
• D. total pressure of the system

Explanation: Rate measures how quickly reactants are consumed or products formed, so its units are usually moles per cubic decimetre per second.

• A. are of the same size
• B. collide with energy equal to or greater than the activation energy and with the correct orientation
• C. collide at low temperature
• D. collide exactly head on, regardless of energy

Explanation: Most collisions are fruitless because the molecules either rebound with too little energy to break existing bonds or meet at the wrong…

• A. the fastest step
• B. the slowest step, which controls the overall rate
• C. always the first step
• D. the step with the largest number of molecules

Explanation: An overall reaction can proceed no faster than its slowest stage, in the same way that a road is only as clear as its narrowest point, so…

• A. the mass of the flask, which falls as carbon dioxide escapes
• B. the colour of the acid
• C. the temperature of the marble
• D. the mass of the flask, which rises as gas is produced

Explanation: Carbon dioxide leaves the open flask, so the total mass decreases steadily and the loss per unit time is a direct measure of the rate.

• A. -d[B]/dt
• B. d[D]/dt
• C. -1/2 d[A]/dt
• D. -1/3 d[C]/dt

Explanation: Rate is expressed as the change in concentration divided by the coefficient, with a minus sign for reactants because they are being…

• A. Separating factors
• B. decreasing factors
• C. Colouring factors
• D. retardation factors

Explanation: The distribution coefficient is the ratio of a solute's concentration in two phases at equilibrium, and differences in this ratio allow…

• A. Catalyst
• B. Intermediate
• C. inhibitor
• D. activated complex

Explanation: An intermediate is formed in one elementary step and consumed in a later step, so it does not appear in the overall reaction equation.

• A. Greater will be dx/dt
• B. Lesser will be dx/dt
• C. dx/dt will be moderate
• D. any of above

Explanation: For a reaction with a positive order, increasing reactant concentration increases the frequency of effective collisions, so the rate dx/dt…

• A. Concentration of reactant does not change
• B. Concentration of product increases
• C. Concentration of reactant decreases
• D. Concentration of reactant increases

Explanation: A negative sign before a reactant concentration change shows that the reactant is being consumed, so its concentration decreases with…

• A. Fast step
• B. Slowest step
• C. All steps
• D. Molecularity of the reaction

Explanation: In a multistep mechanism, the slowest elementary step has the greatest resistance and limits how quickly the overall reaction can proceed.

• A. Moles dm-3 sec-1
• B. Moles dm-3
• C. Moles sec-1
• D. Mol-1 dm3 sec-1

Explanation: Reaction rate is the change in concentration per unit time, so its usual unit is moles dm-3 sec-1.

• A. rate of forward reaction
• B. rate of backward reaction
• C. rate constant
• D. rate co-efficient

Explanation: The conversion of reactants into products per unit time is the rate of the forward reaction, expressed through the decrease in reactant…

• A. very slow
• B. very fast
• C. slow
• D. no regular character present

Explanation: Most organic reactions are relatively slow because covalent bonds are strong and many reactions require significant activation energy or…

• A. Instantaneous rate
• B. Constant rate
• C. Average rate
• D. All of these

Explanation: The rate of reaction between two specific intervals is called the average rate of reaction because it is calculated by taking the change…

• A. 6 x 10^-3mol dm-3 sec-1
• B. 6 x 10^-4 mol dm-3 sec-1
• C. 6 x 10^-2 mol dm-3 sec-1
• D. 6 x 10^-5 mol dm-3 sec-1

Explanation: 𝑟𝑎𝑡𝑒 𝑜𝑓 𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛 = Δ𝐶/𝑡 = (6 × 10−4 )/10 = 6 × 10−5𝑚𝑜𝑙𝑑𝑚−3𝑠𝑒𝑐−1 Given: Change in concentration = 6 x 10^(-4) mol…

• A. Rate = k [NO] [O2]
• B. Rate = k [NO]2[O2]
• C. Rate = k [NO2]2
• D. Rate = k [NO2]

Explanation: The rate equation involves reactants, not products. Assuming the coefficients in the reaction equation represent the orders of reaction…

• A. rate constant
• B. reaction speed
• C. rate of a reaction
• D. All of these

Explanation: The rate of a reaction can be represented as the rate of change of concentrations of either the products or the reactants.

• A. In fraction
• B. Negative
• C. Positive
• D. All of these

Explanation: Rate of reaction = amount of product form/timeA positive sign indicates reaction proceeding in the forward direction, a negative sign…

• A. It is independent of concentration of reactants.
• B. It depends upon the temperature.
• C. It does not depend upon the order of reaction.
• D. All of the above options are correct.

Explanation: Option a) "It is independent of the concentration of reactants" is not true about the rate of reaction.

• A. Reaction time
• B. Reaction Speed
• C. Rate of reaction
• D. All of these options are correct

Explanation: A. Reaction time (Incorrect): Reaction time refers to the time it takes for a reaction to occur, not the rate of the reaction represented…