# How to determine the product of a Chemical Reaction.

Ok the question is some what simple and difficult. I know there are certain rules like

a. A + B = AB (combination)
b. AB = A + B (decomposition)
c. AB + C = CB + A (substitution)
d. AB + CD = AD + CB (metathesis)

now the trouble i have is not in balancing the equation but figuring out what the out come of the reactants will be.

For example an unsolved and unbalanced equation.

___Ca(s) + ____H2O(l) ----> (???)

Why is the answer to the above question Ca(OH)2 + H2 and not CaO + H2.......are there any particular rules i would have to know when figuring out the product of reactants.

Using the rules mentioned above would the following equation be right or wrong

___Al(s) + ____H2O(l) ----> (???)

result: 2Al + 3H2O ---> Al2O3 + 3H2

Also is there anything to do with classification of elements that change the out come of the product.

Thanks!!!

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Both metal oxides and hydroxides are actually correct.

General rule is that, when react with cold water, metal hydroxide is produced whereas oxide is produced if steam is used.

• Govind_Balaji
In the first equation, calcium (which always has +2 charge in solution) will react with the anion formed by water, which is OH(-), not O(2-). Remember that once H2O loses a proton, it becomes a strong base that won't be willing to give up another proton. To balance the charges, one calcium ion accepts two hydroxide ions.

The same could be applied to the second equation. Give it a shot!

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