If the volume of a gas, at constant temperature, changes from 200 ml to 500 ml, the pressure on the gas must have changed from 400 torr to .

160 torr

Explanation:

To calculate the new pressure, we use the equation given by Boyle's law. This law states that pressure is directly proportional to the volume of the gas at constant temperature.

The equation given by this law is:

where,

are initial pressure and volume.

are final pressure and volume.

We are given:

Putting values in above equation, we get:

Thus the pressure has changed to 160 torr

it's filtration, but this is an assumption so my apologies if i got this

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.