Sunday, February 26, 2006
AP Q4 tip from a master
Take this tip from Prof. Adrian Dingle, the grandmaster of all AP Chem teachers:
Subject: Re: symbols used in chemical equations
One more note on balancing equations and question #4 on the exam. Here's a useful tip if you don't appreciate it already.
I teach my kids that non-metal oxide + water ==> acid. They have difficulty remembering which acid is produced. For example, when SO2 is bubbled into water is it H2SO3 or H2SO4? This question is answered by writing a BALANCED equation. I tell them to do that on scratch paper, and record the unbalanced equation on the answer sheet. Simple.
So, regarding his example, you would balance
SO2 + H2O --> H2SO3
which works out as is to a one to one to one ratio; sulfurous acid is weak and should be written as an un-ionized molecule.
For P4O10 (tetraphosphorus decoxide) + H2O --> H3PO4 or H3PO3 ?
with Phosphoric acid, the equation "works" and balances to
P4O10 + 6 H2O --> 4 H3PO4
whereas with H3PO3, the numbers do not balance...
More tips forthcoming as test day approaches.
Subject: Re: symbols used in chemical equations
One more note on balancing equations and question #4 on the exam. Here's a useful tip if you don't appreciate it already.
I teach my kids that non-metal oxide + water ==> acid. They have difficulty remembering which acid is produced. For example, when SO2 is bubbled into water is it H2SO3 or H2SO4? This question is answered by writing a BALANCED equation. I tell them to do that on scratch paper, and record the unbalanced equation on the answer sheet. Simple.
So, regarding his example, you would balance
SO2 + H2O --> H2SO3
which works out as is to a one to one to one ratio; sulfurous acid is weak and should be written as an un-ionized molecule.
For P4O10 (tetraphosphorus decoxide) + H2O --> H3PO4 or H3PO3 ?
with Phosphoric acid, the equation "works" and balances to
P4O10 + 6 H2O --> 4 H3PO4
whereas with H3PO3, the numbers do not balance...
More tips forthcoming as test day approaches.
# posted by C @ 4:23 AM 
