At the top of a mountain the thermometer reads 0$$^\circ$$C and the barometer reads 710 mm Hg. At the bottom of the mountain the temperature is 30$$^\circ$$C and the pressure is 760 mm Hg. The ratio of the density of air at the top to that of the bottom is

The enthalpies of combustion of carbon and carbon monoxide in excess of oxygen at 298 K and constant pressure are $$-$$393.5 kJ/mol and $$-$$280.0 kj/mol respectively. The heat of formation of carbon monoxide at constant volume is