Zn + HCl → H2 +ZnCl2 type of reaction?

Which statement about hf is true? it is zero for any compound in its standard state. it is positive when the bonds of the product store more energy than those of the reactants. it is negative when a compound forms from elements in their standard states. it is zero for any element that is in the liquid state.

Astudent conducts an experiment to determine how the amount of water given to a plant affects its growth. what is the independent variable for this experiment?

If i had 2 m naoh solution, what does the 2 m stand for? 2 molar, but 2 of a solute in 1