How does the hydrogen concentration of a solution change when pH shifts from 6 to 2? 1. The hydrogen concentration has decreased by four times. 2. The hydrogen concentration has increased by four times. 3. The hydrogen concentration has decreased by 10,000 times. 4. The hydrogen concentration has increased by 10,000 times.

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.