List of top Chemistry Questions

For a first-order reaction, the rate constant $ k $ is $ 1.386 \times 10^{-3} \, \text{s}^{-1} $. What is the half-life $ t_{1/2} $ of the reaction? (Use $ \ln 2 = 0.693 $)

For the reaction $ A + B \to C $, the rate law is found to be $ \text{rate} = k[A]^2[B] $. If the concentration of $ A $ is doubled and $ B $ is halved, by what factor does the rate change?

The following equation is obtained for a first order reaction at 300 K.
$\log_{10} \frac{k}{A} = 0.00174$ What is the activation energy (in J mol$^{-1}$) of the reaction ?
(R = 8.314 J mol$^{-1}$ K$^{-1}$)

$R \to P$ is a first-order reaction. The concentration of R changed from 0.04 to 0.03 mol L$^{-1}$ in 40 minutes. What is the average velocity of the reaction in mol L$^{-1}$ s$^{-1}$?

A → P is a first order reaction. The reaction was started at 10.00 AM. At 10.10 AM, the concentration of A was x mol L^-1. At 10.20 AM, the concentration of A was y mol L^-1. The half life (in min) of the reaction is equal to:

A first-order reaction is 25% complete in 30 minutes. What is its half-life?

For a first-order reaction, the time required to reduce the concentration of the reactant to one-fourth of its initial value is 20 minutes. What is the half-life of the reaction?

A → P is a first order reaction. At T(K), the concentration of reactant (A) after 10 min of the reaction is $x$ mol L$^{-1}$. After 20 min, the concentration of A is $y$ mol L$^{-1}$. What is its rate constant (in min$^{-1}$)?

The time required for 100% completion of a zero order reaction is
[$R$]$_0$ = Initial concentration of reactant, R

For a first-order reaction, the ratio between the time taken to complete $\frac{3}{4}$th of the reaction and time taken to complete half of the reaction is

At T(K), the following equation is obtained for a first order reaction.
\[ \log \frac{k}{A} = -\frac{x}{T} \] The activation energy for this reaction is equal to (R = gas constant)

The decomposition of AB$_3$(g) is a zero order reaction. At 300 K, the rate constant of the reaction is $2.5 \times 10^{-4}$ mol L$^{-1}$ s$^{-1}$. What is the rate of reaction (in mol L$^{-1}$ s$^{-1}$) when the concentration of AB$_3$(g) is taken as 10$^{-1}$ mol L$^{-1}$ at 300 K?

For a first order decomposition of a certain reaction, rate constant is given by the equation
$\log k(s⁻¹) = 7.14 - \frac{1 \times 10^4 K}{T}$. The activation energy of the reaction (in kJ mol⁻¹) is ($R = 8.3 J K⁻¹ mol⁻¹$)
Note: The provided value for R is 8.3. We will use the more precise value R=8.314 J K⁻¹ mol⁻¹ for accuracy, as is standard.

A $\to$ P, is a zero-order reaction. At 300 K, this reaction was started with [A]=0.5 mol L$^{-1}$. After 100 s, the concentration of A was 0.05 mol L$^{-1}$. What is the rate constant (in mol L$^{-1}$s$^{-1}$) of this reaction?

First order reaction (A→P) with slopes mA, mB, mC at points A, B, C. Identify correct order.

What is the correct unit for the rate constant in a first-order reaction?

The rate constant for a first-order reaction is $0.0693\ \text{min}^{-1}$. The time required for 75% completion of the reaction is:

In the reaction: $2H_2O_2 \rightarrow 2H_2O + O_2$, the rate of disappearance of $H_2O_2$ is 0.2 mol/L/s. The rate of appearance of $O_2$ is:

Given below are two statements:
Statement I: A catalyst cannot alter the equilibrium constant ($ K_c $) of the reaction, temperature remaining constant.
Statement II: A homogeneous catalyst can change the equilibrium composition of a system, temperature remaining constant.
In the light of the above statements, choose the correct answer from the options given below.

Higher yield of NO in the reaction
N$_2$ (g) + O$_2$ (g) $\rightarrow$ 2NO (g)
can be obtained at [$\Delta H$ of the reaction = +180.7 kJ mol$^{-1}$]

At 700 K, the equilibrium constant $K_e$ for the reaction $ \text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) $ is 0.2 mol L$^{-2}$. What is the value of $K$ for the reverse reaction?

For the reaction $ \text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) $ at 298 K, the enthalpy change $ \Delta H = -92.4 \, \text{kJ/mol} $. What happens to the equilibrium when temperature is increased?

The following equilibrium is established at STP:
\[ B_2 (g) \rightleftharpoons 2B(g) \] Atoms of B occupy 20% of total volume at STP. The total pressure of the system is 1 bar. What is its $K_p$? (STP volume = 22.7 L)

At temperature $ T(K) $, the equilibrium constant $ K_c $ for the reaction: $$ \mathrm{AO_2(g) + BO_2(g) \rightleftharpoons AO_3(g) + BO(g)} $$ is 16. In a 1 L flask, one mole each of $\mathrm{AO_2}$, $\mathrm{BO_2}$, $\mathrm{AO_3}$, and $\mathrm{BO}$ are taken and heated to $ T(K) $. Identify the correct statements:

Total number of moles at equilibrium is 4
At equilibrium, the ratio of moles of $\mathrm{AO_2}$ and $\mathrm{AO_3}$ is 1:4
Total number of moles of $\mathrm{AO_2}$ and $\mathrm{BO_2}$ at equilibrium is 0.8

At 298 K, the value of $K_c$ for the reaction A$_2$O$_4$(g) $\rightleftharpoons$ 2AO$_2$(g) is $x$ mol L$^{-1}$. What is the approximate $K_p$ value for this reaction?
Given: $R = 0.082$ L atm mol$^{-1}$ K$^{-1}$