Dena A. answered • 08/03/15
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Former Chemistry Department Head with 10+ Years of Tutoring Experience
STEP 1:
Sodium is an alkali METAL with a +1 charge.
OXIDE is an anion with a -2 charge.
You should memorize the charges (common oxidation states) by looking at the families on the periodic table. (:
So, if it's Na+1 with O-2, we criss-cross the charges to get the sub-scripts. So we get Na2O.
STEP 2:
Water is H2O, as I am sure you know. So we are done with the reactant's side: Na2O + H2O
STEP 3:
So, here's where the fun part comes in. You need to memorize various types of reactions. One type is ANY METAL OXIDE ADDED TO WATER MAKES A STRONG BASE. The moment you saw sodium METAL and the OXIDE anion, your brain should go "ding! ding!" (I suggest making flashcards of the various types of reactions in your book) and you should think...IT MAKES A STRONG BASE!
STEP 4:
To write the base, you put Na+1 with a HYDROXIDE anion (OH-) which you need to also memorize.
So, Na+ and OH- cancel their charges and you simply get NaOH.
STEP 5:
We're not done yet. You have to BALANCE the final equation. We have Na2O + H2O --> NaOH. We have 2 sodiums and 2 oxygens and 2 hydrogens on the left side, but only one of each on the right side. So we have to multiply the entire right species by a coefficient of 2.
FINAL ANSWER:
Na2O + H2O --> 2NaOH
Hope this helps!! I used to help my students online all the time.
Dena A.
Oh that's usually where students go wrong! They spend all their time memorizing the binomials and how to write the formulas that they forget to memorize the reaction types! Nine times out of ten, there will be a big fat page in your book with a list of reaction types that you have to memorize. If you can't find it, I encourage you to ask your teacher to make a compiled list for you. I used to make colorful chinese fans with my chemistry students with the reaction types on one side and examples on the other. As ridiculous as it sounds, anything to make them stick is a good thing!!
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08/04/15
Dena A.
Also Mathalina, when you practice this specific type of reaction, don't just practice with alkali metal oxides. For example, try giving me Magnesium oxide in water and see if you can come up with the balanced equation for that one (it's a bit trickier!).
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08/04/15
Mathalina S.
Thanks for all your help and advice! I would definitely get lessons from you if I lived in your area.
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08/04/15
Joe B.
Also Na and NaH are very reactive, so they usually won't end up on the products side of a synthesis reaction.
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10/23/16
Mathalina S.
08/03/15