Acomputer monitor uses 200 w of power. how much energy does it use in
10 seconds?

2000 Joules.

Explanation:

Wattage = Energy / t

Energy is in joules

wattage is in watts

t is in seconds.

W = 200 watts

E =

t = 10 seconds

E = W * t

E = 200 * 10

E = 2000 Joules

if you mean hydrogen and oxygen then water is the product

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.