Ascientist observed changes in the gas pressure of one mole od a grass in a sealed chamber with a fixed volume. to identify the source of the change, the scientist should check for variations in the
a. air pressure
b. molecular formula
c. temperature of the chamber
d. isotopes of the gas

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.

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.