4. Average kinetic energy depends only on temperature. So answer is E.
5. PV=m/M*RT--ideal gas law. m=d*V, where d is density. So PM=dRT. Product of molar mass M and pressure is greatest for container B, since 4*30=120>2*58=116. Hence answer is B.
6. Butane will condense the first, since its molecules move with slowest speed. Answer is D.