Which of the following series of transitions in the spectrum of hydrogen atom falls in visible region?

The unit of rate constant for a first-order reaction is:

For the reaction 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), ΔH = -198 kJ. Which condition favours forward reaction?

The standard heat of formation, in $\mathrm{kcal} / \mathrm{mol}^{\text {of }} \mathrm{Ba}^{2+}$ is : [Given : standard heat of formation of $\mathrm{SO}_4^{2-}$ ion (aq) $=-216 \mathrm{kcal} / \mathrm{mol}$, Standard heat of crystallisation of $\mathrm{BaSO}_4(\mathrm{~s})=-4.5 \mathrm{kcal} / \mathrm{mol}$, standard heat of formation of $\left.\mathrm{BaSO}_4(\mathrm{~s})=-349 \mathrm{kcal} / \mathrm{mol}\right]$

Match List - I with List - II $\begin{array}{llll} & \begin{array}{l} \text { List-I } \\ \text { (Example) } \end{array} & & \begin{array}{l} \text { List-II } \\ \text { (Type of Solution) } \end{array} \\ \text { A. } & \text { Humidity } & \text { I. } & \text { Solid in solid } \\ \text { B. } & \text { Alloys } & \text { II. } & \text { Liquid in gas } \\ \text { C. } & \text { Amalgams } & \text { III. } & \text { Solid in gas } \\ \text { D. } & \text { Smoke } & \text { IV. } & \text { Liquid in solid } \end{array}$ Choose the correct answer from the options given below:

The conjugate base of H₂SO₄ is: