For the chemical reaction X $$\rightleftharpoons$$ Y, the standard reaction Gibbs energy depends on temperature T (in K) as $$\Delta $$_rG^o (in kJ mol^–1) = 120 $$ - {3 \over 8}$$ T.

The major component of the reaction mixture at T is :

A solid having density of 9$$ \times $$10³ kg m^–3 forms face centred cubic crystals of edge length $$200\sqrt 2 $$ pm. What is the molar mass of the solid?
[Avogadro constant $$ \cong $$ 6 $$ \times $$ 10²³ mol^–1 , $$\pi $$ $$ \cong $$ 3]

Heat treatment of muscular pain involves radiation of wavelength of about 900 nm. Which spectral line of H atom is suitable for this purpose?

[R_H = 1 $$ \times $$ 10⁵ cm^–1, h = 6.6 $$ \times $$ 10^–34 Js, c = 3 $$ \times $$ 10⁸ ms^–1]

An organic compound is estimated through Duma's method and was found to evolve 6 moles of CO₂. 4 moles of H₂O and 1 mole of nitrogen gas. The formula of the compound is :