Which of the following pairs constitutes a buffer?
Held on 30 Apr 2006 · Verified 9 Jul 2026.
HCl and KCl
HNO2 and NaNO2
NaOH and NaCl
HNO3 and NH4NO3
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For the reaction 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), ΔH = -198 kJ. Which condition favours forward reaction?
The unit of rate constant for a first-order reaction is:
The conjugate base of H₂SO₄ is:
Phosphoric acid ionizes in three steps with their ionization constant values $\mathrm{K}_{\mathrm{a}_1}, \mathrm{~K}_{\mathrm{a}_2}$ and $\mathrm{K}_{\mathrm{a}_3}$, respectively, While K is the overall ionization constant. Which of the following statements are true? A. $\log \mathrm{K}=\log \mathrm{K}_{\mathrm{a}_1}+\log \mathrm{K}_{\mathrm{a}_2}+\log \mathrm{K}_{\mathrm{a}_3}$ B. $\mathrm{H}_3 \mathrm{PO}_4$ is a stronger acid than $\mathrm{H}_2 \mathrm{PO}_4^{-}$and $\mathrm{HPO}_4^{2-}$ C. $K_{a_1}\gt K_{a_2}\gt K_{a_3}$ D. $\mathrm{K}_{\mathrm{a}_1}=\frac{\mathrm{K}_{\mathrm{a}_3}+\mathrm{K}_{\mathrm{a}_2}}{2}$ Choose the correct answer from the options given below:
If the half-life $\left(\mathrm{t}_{1 / 2}\right)$ for a first order reaction is 1 minutes, then the time required for $99.9 \%$ completion of the reaction is closest to:
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