In the combustion chamber of an engine, the initial volume is 450 cm3 at a pressure of 1.0 atmosphere. if the piston displaces 402 cm3 of the total, what is the resulting pressure in the combustion chamber? (assume negligible temperature change.) hint: calculate the new volume by subtracting the amount of space the piston takes up from the initial volume. atm

Assuming that the contents of the chamber ar ideal gases. We can use the relation PV=nRT.  At a constant temperature and number of moles of the gas the product of PV is equal to some constant. At another set of condition of temperature, the constant is still the same. Calculations are as follows:

P1V1 =P2V2

P2 = (1)(450)/ 48

P2 = 9.375 atm

if you mean hydrogen and oxygen then water is the product