0.4 g mixture of NaOH, Na₂CO₃ and some inert impurities was first titrated with $${N \over {10}}$$ HCl using phenolphthalein as an indicator, 17.5 mL of HCl was required at the end point. After this methyl orange was added and titrated. 1.5 mL of same HCl was required for the next end point. The weight percentage of Na₂CO₃ in the mixture is ________. (Rounded off to the nearest integer)

In basic medium $$Cr{O_4}^{2 - }$$ oxidises $${S_2}{O_3}^{2 - }$$ to form $$S{O_4}^{2 - }$$ and itself changes into $$Cr{(OH)_4}^ - $$. The volume of 0.154 M $$Cr{O_4}^{2 - }$$ required to react with 40 mL of 0.25 M $${S_2}{O_3}^{2 - }$$ is __________ mL. (Rounded off to the nearest integer)

Consider the following chemical reaction.


The number of sp² hybridized carbon atom(s) present in the product is ________.

A car tyre is filled with nitrogen gas at 35 psi at 27$$^\circ$$C. It will burst if pressure exceeds 40 psi. The temperature in $$^\circ$$C at which the car tyre will burst is _________. (Rounded off to the nearest integer)