Gloamy's Chemistry Questions

[Gloamglozer]

I know some of these questions may like infants could do these in their sleep but I was doing some revision and I got stuck with some of these questions.  Can someone please help me?

1.  Find the oxidation number of N atoms in .

Done.  Thank you Edmund, chem-nerd and Dark Horse.


2.  When acidified orange potassium dichromate () is added to ethanol () the final solution is green and there is the distinct odour of vinegar.  It is shown to contain ions and ethanoic acid ().

Write balanced half equations for this reaction and use them to write the overall equation for the reaction.

Thank you Edmund, chem-nerd and coblin.


3.  In the 19th century, relative atomic masses (RAMs) were determined by gravimetric analysis.  In a particular experiment, to determine the RAM of a metal (X), 3.27 g of X was completely reacted with oxygen to produce 4.07 of the oxide of formula XO.  The RAM of X is:

A.  12.8
B.  32.7
C.  65.4
D.  130.8

It makes sense now.  Thank you chem-nerd & Edmund.


4.  Carbon monoxide reacts with oxygen as follows:
If of CO and of are mixed at constant temperature and pressure, the final volume of gas in the mixture will be:

A. 
B. 
C. 
D. 

Understood.  Thank you chem-nerd & Edmund.

[jaja]

do different isomers give different spectra for mass and IR spectrometry?

[Edmund]

1.

Oxidation number for Oxygen = -6, Hydrogens = +4

Total Oxidation number for molecule = 0

N + (+4) + (N) + (-6) = 0
N = +1



2.




(Not sure if the oxidation equation is right.)

Then Balance.




3. C. 65.4

X  +  O    ------>   XO

Mole ratio of X:XO is 1:1

=

We know M(O) = 16

Solve for M(X)

brb

4.
At constant temperature and pressure, volume is proportional to number of moles.

V = an, where a is a constant.

a =

+ = 150

[chem-nerd]

hmm, brain on a sugar high from too many easter eggs so this answer may be dubious

1. two different ONs for N in this compound NH₄NO₃
    N -3 N +5

 Edit: yep definitely too much sugar. thanks dark horse

[Edmund]

hmm, brain on a sugar high from too many easter eggs so this answer may be dubious

1. two different ONs for N in this compound NH₄NO₃
    N +3 N -5

 

oh yea

[Dark Horse]

Hang on, do you mean -3 and +5?    lol, I need a sugar hit right now

[Edmund]

Charge on H is +4, on whole molecule is +1

Therefore Oxi. Number for N is -3



Oxi number will be +5

[monokekie]

which txt book is it?

[Gloamglozer]

1. 

Charge on H is +4, on whole molecule is +1

Therefore Oxi. Number for N is -3



Oxi number will be +5

Ah, so you need to split it up to work it out.  Thanks Edmund.


2.  The answers say:



I was like, "How on Earth did that happen?"


3. 

3. C. 65.4

X  +  O    ------>   XO

Mole ratio of X:XO is 1:1

=

We know M(O) = 16

Solve for M(X)

Oh ok.  But at this point am I allowed to do this:

=

?


4. 

At constant temperature and pressure, volume is proportional to number of moles.

V = an, where a is a constant.

a =

+ = 150

I don't quite get this one.  How did you get:

V = an

I thought that if:

1.  Every chemical present is a gas;
2.  The temperature and pressure are constant;

then the coefficients represent the volumes of gas reacting, which I can sort of see that you've done.  Can you please elaborate?

which txt book is it?

These were some questions from tutoring that I do.  I haven't seen them pop up in the Heinemann textbook.  I'm not sure about the other textbooks though (such as Jacaranda, Chemistry Dimensions, etc.)

[chem-nerd]

2. (Cr₂O₇^2-(aq) + 14H⁺(aq) + 6e- -> 2Cr³⁺(aq) + 7H₂O(l)) x 2

(C₂H₅OH(aq) + H₂O(l) -> CH₃COOH(aq) + 4H⁺(aq) + 4e-) x 3

then subtract the H₂0s and H⁺s that appear on both sides

3. n(X) : n(O) is 1:1 so it would be just as easy to do
     3.27/M(X) = 0.8/M(O)

4. you can think of it as 100mol of CO reacting with 100mol of O₂ to form 100mol of CO₂ in a 2:1:2 ratio. thus O₂ is in excess by 50mol and 100mol of CO₂ is formed. thus the final volume would be 150cm³

[Gloamglozer]

2.  I've pretty much got it, except for one thing.  Instead of getting , I've left it as .  I know they are the same thing but can the answers do that?


3.  Thanks, I got it.


4.  Now I get it.  Thanks again.  After reading your explanation, I get what Edmund was trying to say.

[Collin Li]

2.  I've pretty much got it, except for one thing.  Instead of getting , I've left it as .  I know they are the same thing but can the answers do that?

Personally I would also use .

The difference is that one is the semi-structural formula (it shows a bit of the structure) and one is merely the molecular formula.

Both are fine, unless you are specified to do one over the other (they usually don't specify "semi-structural", but instead want the full structural formula, if they're going to ask for it).

[Gloamglozer]

Thanks coblin for clearing that up.