|By Tigerswinter (Tigerswinter) on Friday, June 04, 2004 - 10:01 pm: Edit|
Here are some questions that I always get confused on. It might help you too.
1) How do you know which is the cathode and the anode. Yes, cathode is where the reduction occurs and the anode is where the oxidation occurs, but on some questions the + is on the left side and it gets all confusing at the end.
ex) Barrons Sample Test 2 #70.
2) Which nonmetals are not gases at STP ?
3) Are all noble gases .. --> gases at STP ?
4) CH4 : It is true that CH4 has polar covalent bonds, but they cancel each other out and results in a nonpolar molecule ? So, would you call this a polar covalent compound or nonpolar convalent compound ?
5) Who discovered electrons, neutrons, protons, nucleus ?
6) Barrons Practice Test 3 - # 5 ~ 7 (dealing, again with cathode, anode)
7)Do transition metals have complete outer energy levels ?
8) When a crystal is added to a supersaturated solution of itself, the crystal does not change. TRUE OR FALSE ?
9) How do you know if a gas is heavier/lighter than air ??
Yeah, these ARE pretty tricky, and they're definately on the test tomorrow.
|By Mahras (Mahras) on Friday, June 04, 2004 - 10:26 pm: Edit|
1. Electrochem cell: cation=reduc. anion=oxidation
Electrolytic cell: cation=oxidation anion=reduction
2. Only Br (Bromine) is a liquid at STP.
3. All noble gasses are gases at STP.
4.Yes. CH4 has structural symmetry thus cancelling each sides polarity with the other side to create a nonpolar compound
5.Common its in chapter 2 and three. read the book.
6. see number 1
7. NOPE. Transition metals are called TRANSITION metals because they are in TRANSITION to get a complete outer energe shell. Get it!!!*corny joke*
8. Crytal does change. This is because crystallization occurs.
9. I have no idea. ahaha.
Okay I took that test and i also took a real test from the 22 real SAT IIs. That test is hard. Got a 720-700 range for that (though I took it while I was riding the subway) and then took the real one and got a 780. So, if you got a 700+ you ll get a high score.
Good luck to you and me!!!(I am also taking chem)
|By Thunder77 (Thunder77) on Friday, June 04, 2004 - 11:08 pm: Edit|
Ok, I'm all prepared now for the Chem test so I'll be kind and help out
The + and - signs are DIFFERENT in electrochemical and galvanic(voltaic) cells.
In Electrochemical cells, the anode is + and the cathode is -. why? Electricity is going tothe cathode, which makes it negative, and the anode is considered positive because of this
In galvanic(voltaic) cells, the anode is - and the cathode is +!! why? Since in voltaic cells the electron flow comes OUT of the anode INto the cathode, the anode is considered to be the source of negative charges so it is designated -.
As for whether a gas is heavier than air, I always found it useful to find its molar mass first. then I compare it to 22.4. If its less, then the gas is lighter than air. If its more, then its heavier. I'm pretty sure 22.4 is a BAD number to compare it with, but since the numbers are either very small like 2, 8, or either very large 40 or 60, it is easy to differentiate between them. Though my method may be faulty, it works everytime on every question !!
Hope you my help and do well. I usually dont take the time to type up long explanations. 800 !
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