[imari]

I have a bunch of AP Chem questions and although I have been able to answer some of them, there are a few that i can't figure out! I want to stay on top of things, how can I do these problems? 



1. A 5.025 g sample of Ca is burned in air to produce a mixture of two ionic compounds, calcium oxide and calcium nitride. Water is added to the mixture. It reacts with the calcium oxide to for 4.832 g of calcium hydroxide. How many grams of calcium oxide were formed? How many grams of calcium nitride?

- I started out with:
            Ca + ____ --> CaO + Ca2N2
            5.025 g           ?         ?

            CaO + Ca2N2 + H2O --> Ca(OH)2 + ___
              ?          ?                    4.8325
- I figure I can convert the Ca to moles, and then see that its a 1:1 ratio between everything (so I know I have that amount of moles of everything) but do I have enough of a balanced equation to assume that?



2. Suppose that the spin quantum number could have the values 1/2, 0, and -1/2. Assuming that the rules governing the values of the other quantum numbers and the order filling sublevels were unchanged,
     a) what would be the electron capacity of a s, p, and d sublevel?
          -My logic? s sublevel = 0 which has 2 electrons
                         p " = -1/2, 0, 1/2 which would have 1+2+1= 4 electrons
                        d " = 1,1/2,0,-1/2,-1 which would have 2+1+2+1+2= 8 electrons
     b) how many electrons could fit in the n=3 level?
           - 3s   3p   3d
              2 + 4 + 8 = 14
     c) what would be the electron config of the element with atomic number 8?17?
           - atomic #8= 1s2 2s2 2p4
             atomic #17= 1s2 2s2 2p4 3s2 3p4 4s2 3d1

[DevaDevil]

- I started out with:
            Ca + ____ --> CaO + Ca2N2
            5.025 g           ?         ?

            CaO + Ca2N2 + H2O --> Ca(OH)2 + ___
              ?          ?                    4.8325
- I figure I can convert the Ca to moles, and then see that its a 1:1 ratio between everything (so I know I have that amount of moles of everything) but do I have enough of a balanced equation to assume that?

Calcium Nitride, to the best of my knowledge is C₃N₂, it is formed from calcium and nitrogen as a byproduct from the burning.

And the second part is a bit strange. I think they want you to assume the water only reacts with CaO to form the hydroxide (with calcium nitride as inert product). But water also reacts with the calcium nitride to form calcium hydroxide and ammonia...




I am very rusty on the second part of your question, but I hope someone else may answer that part of your question.

[Yggdrasil]

2. Suppose that the spin quantum number could have the values 1/2, 0, and -1/2. Assuming that the rules governing the values of the other quantum numbers and the order filling sublevels were unchanged,
     a) what would be the electron capacity of a s, p, and d sublevel?
          -My logic? s sublevel = 0 which has 2 electrons
                         p " = -1/2, 0, 1/2 which would have 1+2+1= 4 electrons
                        d " = 1,1/2,0,-1/2,-1 which would have 2+1+2+1+2= 8 electrons
     b) how many electrons could fit in the n=3 level?
           - 3s   3p   3d
              2 + 4 + 8 = 14
     c) what would be the electron config of the element with atomic number 8?17?
           - atomic #8= 1s2 2s2 2p4
             atomic #17= 1s2 2s2 2p4 3s2 3p4 4s2 3d1

I think you may be confusing the magnetic quantum number (m_l = -L, -L+1, ... , -1, 0, 1, ...,L-1, L) with the spin quantum number (m_s = -1/2 or +1/2).

[Borek]

In the first question you don't have one reaction for burning - you have two separate processes. Otherwise I am with DevaDevil on this one - question is a little bit strange, you are probably expected to assume that calcium nitride doesn't react with water - even if in reality it does

[DevaDevil]

I think you may be confusing the magnetic quantum number (m_l = -L, -L+1, ... , -1, 0, 1, ...,L-1, L) with the spin quantum number (m_s = -1/2 or +1/2).

Yeah I thought that initially too, but then I wondered if the question was meant to be read as: In real life m_s = -1/2, 1/2; suppose it could have the values -1/2, 0, 1/2, with all the other level ruling the same, what would then be... etc etc

[Yggdrasil]

That's exactly how I interpret the problem.