List of top Chemistry Questions

A drop of solution (Volume 0.05 mL) contains $ 3.0 \times 10^{-6} $ moles of H$^+$ ions. If the rate constant of disappearance of H$^+$ is $ 1.0 \times 10^{-7} \, \text{mol litre}^{-1} \text{sec}^{-1} $, how long will it take for H$^+$ ions to disappear?

Match the details given in Column I with those given in Column II:

Choose the correct order of increasing acidic strength of the following compounds.

A first-order reaction has the rate constant of $1.15 \times 10^{-3} \, \text{s}^{-1}$. The time required to reduce 10 g of reactant to 6 g is $x \times 10^2$ sec. What is the approximate value of $x$?

Consider the reaction carried out at T(K):
$\text{A(g) + B(g) → C(g)}$
$\text{The rate law for this reaction is \(r = k[A]^2[B]^2$}\). The concentration of A in experiment 2 and rate in experiment 3 shown as $x$ and $z$ in the table. $x$ and $z$ are respectively:\[\begin{array}{|c|c|c|c|} \hline \text{Experiment} & [A]~(\text{mol L}^{-1}) & [B]~(\text{mol L}^{-1}) & \text{Initial rate (mol L}^{-1} \text{s}^{-1}) \\ \hline 1 & 0.05 & 0.05 & R \\ 2 & x & 0.05 & 2R \\ 3 & 0.20 & 0.10 & z\\ \hline \end{array}\]

If the standard enthalpy change ($\Delta H^o$) for reaction \[ \text{H}_2(g) + \text{Br}_2(l) \rightarrow 2 \text{HBr}(g) \] is $-72.8 \, \text{kJ}$, the standard enthalpy of formation ($\Delta H_f^o$) of $\text{HBr}(g)$ in $\text{kJ mol}^{-1}$ is:

At $ T(K) $, the equilibrium constant for $ A (g) \rightleftharpoons B (g) $ is $ 10^2 $. If the rate of forward reaction is 0.025 mol L$^{-1}$ s$^{-1}$, the rate of backward reaction (in mol L$^{-1}$ s$^{-1}$) is

20 mL of 0.1 M HCl is added to 30 mL of 0.1 M NaOH. To this solution, extra 50 mL of water was added. What is the molarity of the final solution formed?

The rate constant, $ k $, of a zero order reaction $ 2 \text{NH}_3 (g) \xrightarrow{P_{1130K}} \text{N}_2 (g) + 3 \text{H}_2 (g) $ is $ y \times 10^{-4} \, \text{mol} \, \text{L}^{-1} \, \text{s}^{-1} $. The rate of formation of hydrogen (in mol L$^{-1}$ s$^{-1}$) is

The molarity of the solution when 4.9 g of H$_2$SO$_4$ is dissolved in 250 mL of solution is

If the time required for 40% completion of a first order reaction is 50 minutes, what is the time required for completion of 80% of the same reaction?
($ \log 2 = 0.3010, \log 5 = 0.6990, \log 6 = 0.7782 $)

Given below are two statements
Assertion (A): A catalyst generally increases the rate of a reaction
Reason (R): It lowers the activation energy of a reaction by providing a new path

Which of the following correctly represents the integrated rate law equation for a first order reaction in the gas phase?

Which of the following correctly represents integrated rate law equation for a first order reaction in gas phase:

Consider the following equilibrium, $$ 2 \text{NO}(g) \rightleftharpoons \text{N}_2 (g) + \text{O}_2 (g); K_1 = 2.4 \times 10^{20} $$ $$ \text{NO}(g) + \frac{1}{2} \text{Br}_2 (g) \rightleftharpoons \text{NOBr}(g); K_2 = 1.4 $$ Calculate $ K_C $ for the reaction, $$ \frac{1}{2} \text{N}_2 (g) + \frac{1}{2} \text{O}_2 (g) + \frac{1}{2} \text{Br}_2 (g) \rightleftharpoons \text{NOBr}(g) $$

Given below are two statements
Statement I: The changes in pH with temperature are so small that we often ignore it
Statement II: When the hydrogen ion concentration changes by a factor of 100, the pH changes by one unit
In the light of above statements, identify the correct answer from the options given below

At 1000 K, the value of $K_c$ for the below reaction is $10 \text{ mol L}^{-1}$. Value of $K_p$ (in atm) is (given $R = 0.082 \text{ atm L mol}^{-1} \text{K}^{-1}$)
${\{A(g) <=> B(g) + C(g)}$

The equilibrium constants for the reactions a, b, and c are as given:
a) N$_2$ + 3H$_2$ = 2NH$_3$ : K$_1$
b) N$_2$ + O$_2$ = 2NO : K$_2$
c) 2H$_2$ + O$_2$ = 2H$_2$O : K$_3$
What would be the equilibrium constant for the reaction:
4NH$_3$ + 5O$_2$ = 4NO + 6H$_2$O; K$_x$

Observe the following equilibrium $$\text{Fe}^{3+}(aq) + \text{SCN}^-(aq) \rightleftharpoons [\text{Fe(SCN)}]^{2+}(aq)$$ yellow \hspace{1cm colourless \hspace{1cm} deep red}
Addition of aqueous oxalic acid solution to the above equilibrium

One mole of $ PCl_5(g) $ was heated in a 1L closed flask at 500 K. At equilibrium, 0.1 mole of $ Cl_2(g) $ was formed. What is its $ K_p $ (in atm)? (Given R = 0.082 L atm mol$^{-1} $ K$^{-1} $)

One mole of $ A (g) $ is heated to $ T(K) $ till the following equilibrium is obtained \[ A(g) \rightleftharpoons B(g) \] The equilibrium constant of this reaction is $ 10^{-1} $. After reaching the equilibrium, 0.5 moles of A (g) is added and heated. The equilibrium is again established. The value of $ \left[\frac{A}{B}\right] $ is

One mole H\textsubscript{2O(g) and one mole CO(g) are taken in 1L flask and heated to 725K. At equilibrium, 40\% (by mass) of water reacted with CO(g) as follows:} \[ \text{H}_2\text{O(g)} + \text{CO(g)} \rightleftharpoons \text{H}_2\text{(g)} + \text{CO}_2\text{(g)} \] Its $K_c$ value is

Observe the following species \[ \text{AlCl}_3, \, \text{NH}_3, \, \text{H}^+, \, \text{Co}^{3+}, \, \text{OH}^-, \, \text{H}\text{Mg}^{2+}, \, \text{BF}_3, \, \text{Cl}^- \] How many Lewis bases are present in the above list?

At T(K), the $K_p$ for the reaction $A_2B_6(g) \rightleftharpoons 2A_2B_4(g) + B_2(g)$ is 0.04 atm. The equilibrium pressure (in atm) of $A_2B_6(g)$ when it is placed in a flask at 4 atm pressure and allowed to come to above equilibrium is

At 300 K, the total pressure of the following system is 2 atm, at equilibrium: \[ \text{A}_2(g) \rightleftharpoons 2\text{A}(g) \] The atoms of A occupy 20% volume at STP. The $K_c$ of the system is approximately (Given: R = 0.082 L atm mol$^{-1}$ K$^{-1}$, STP volume of 1 mole of a gas = 22.7 L)