A sample of gas absorbs $$4000 \mathrm{~kJ}$$ of heat and surrounding does $$2000 \mathrm{~J}$$ of work on sample. What is the value of $$\Delta U$$ ?

What is the value of $$\mathrm{C}-\mathrm{O}-\mathrm{H}$$ bond angle in $$\mathrm{CH}_3-\mathrm{OH}$$ ?

What is the molarity of solution containing $$3.2 \mathrm{~g}$$ of $$\mathrm{NaOH}$$ (molar mass $$40 \mathrm{~g} \mathrm{~mol}^{-1}$$) in $$250 \mathrm{~cm}^3$$ of water?

A metallic element crystallises in simple cubic lattice. If edge length of the unit cell is $$3\mathop A\limits^o$$, with density $$8 \mathrm{~g} / \mathrm{cc}$$, what is the number of unit cells in $$100 \mathrm{~g}$$ of the metal?

(Molar mass of metal $$=108 \mathrm{~g} / \mathrm{mol}$$ )