What are the oxidation numbers of S atoms in $$\mathrm{S}_4 \mathrm{O}_6^{2-}$$ ?
50 g of a substance is dissolved in 1 kg of water at $$+90^{\circ} \mathrm{C}$$. The temperature is reduced to $$+10^{\circ} \mathrm{C}$$. The density is increased from 1.1 to $$1.15 \mathrm{~g} \mathrm{~cc}^{-1}$$. What is the % change of molarity of the solution?
Identify the correct statements from the following.
I. At 0 K , the entropy of pure crystalline materials approach zero.
II. Entropy for the process, $$\mathrm{H}_2 \mathrm{O}(\mathrm{l}) \longrightarrow \mathrm{H}_2 \mathrm{O}(\mathrm{g})$$ decreases.
III. Gibb's energy is a state function.
Use the data from table to estimate the enthalpy of formation of $$\mathrm{CH}_3 \mathrm{CHO}$$.
| Bond enthalpy | Bond | Enthalpy of formation |
|---|---|---|
| $$\mathrm{400~kJ~mol^{-1}}$$ | $$\mathrm{C-H}$$ | $$\mathrm{C}(\mathrm{g}) 700 \mathrm{~kJ} \mathrm{~mol}^{-1}$$ |
| $$\mathrm{350~kJ~mol^{-1}}$$ | $$\mathrm{C-C}$$ | $$\mathrm{H}(\mathrm{g}) 200 \mathrm{~kJ} \mathrm{~mol}^{-1}$$ |
| $$\mathrm{700~kJ~mol^{-1}}$$ | $$\mathrm{C=O}$$ | $$\mathrm{O}(\mathrm{g}) 250 \mathrm{~kJ} \mathrm{~mol}^{-1}$$ |
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