ssNake's Chemistry [u3] Q's

[REBORN]

Q - When drawing structural formulas of organic compounds (eg propene) can you draw all bonds at right angles or does it have to be correct (eg propene has a planar shape due to double bond...)

Q - How do we name/what VCAA wants? Eg - aminoethane or ethanamine

[pi]

Q - When drawing structural formulas of organic compounds (eg propene) can you draw all bonds at right angles or does it have to be correct (eg propene has a planar shape due to double bond...)

Q - How do we name/what VCAA wants? Eg - aminoethane or ethanamine

1) Either

2) I prefer the second one

[REBORN]

Systematic name for (CH3)₂C=CH₂

Where = resembles the double bond

?

[pi]

Systematic name for (CH3)₂C=CH₂

Where = resembles the double bond

?

2-methyl ethene (or maybe even 'methy ethene' will suffice as there is only one possible way to have this)

Methyl propane, my bad (silly mistake)

[REBORN]

Are you sure that works?

I got Methylpropene.

(I have no answers :/)

[pi]

Are you sure that works?

I got Methylpropene.

(I have no answers :/)

Oh yeah, thats right, didn't see the C next to the methyl

[REBORN]

Q - Cyclic molecules. Cyclohexane is C₆H₁₂.       I thought -ane means single bonds hence 2n+2 so it should be H₁₄

How does this work?

Q - Reaction pathway of Ethene --> Ethylamine

My ans is: Ethene (+Cl2)--> Chloroethane (+NH3) --> Ethyl amine

Provided ans is: Ethene (+water) --> Ethanol (+NH3) --> Ethyl amine

Both are right or..?

[Russ]

Cyclic molecules are different because you've got an extra C-C bond which takes up the space of two C-H bonds, so you need to adjust your rule.

And if you're producing chloroethane, the NH3 addition will only replace one of them?

[REBORN]

I don't understand re-q2.

C2H5Cl + NH3 will give C2H5NH2 which is what we want? :S

[pi]

Q - Cyclic molecules. Cyclohexane is C₆H₁₂.       I thought -ane means single bonds hence 2n+2 so it should be H₁₄

Don't remember chem via random formulas like this. This only applies to straight-chained hydrocarbons. Cyclic version of an alkane is 2n.

How does this work?

Q - Reaction pathway of Ethene --> Ethylamine

My ans is: Ethene (+Cl2)--> Chloroethane (+NH3) --> Ethyl amine

Provided ans is: Ethene (+water) --> Ethanol (+NH3) --> Ethyl amine

Both are right or..?

Forgot all this stuff, but I'll have a go. If +Cl2, you could also get 1,2-dichloroethane in large amounts, which wouldn't work. You want to get the most yield of the desired product as possible, hence, you would react it H2O to get ethanol and substitute the -OH with a reaction with ammonia (with a suitable catalyst, oxide catalyst? I don't remember very well).

[REBORN]

5g of nitrogen is completely converted into an oxide of nitrogen. The mass of the oxide formed is 19.3g. Empirical formula of the oxide?

---

Molar volume of oxygen in L at 1atm and 100deg is closest to: 30.6,24.5,22.4,8.2?

[Hamdog17]

n(N)=5/14=0.357mol
19.3-5=14.3 :. n(O)=14.3/16=0.893mol

n(N):n(O)     0.357:0.893     1:2.5
:.   2:5.   :.   Empirical formula is N2O5


(Assuming you meant 100 degrees Celsius)
General gas eqn.  pV=nRT.    Transpose for V. Use n=1 as molar volume is litres per mole.
V=nRT/p.  V=(1*8.31*(100+273))/101.3.    V=30.6 L.   Therefore molar volume is 30.6L/mol

[REBORN]

^ Thanks.

Q - An analysis is carried out on a sample of unknown gas. The density of the gas is 2.86g/L at STP. The molecular formula of the gas is:
A) HCl
B) Cl2
C) NO2
D) SO2

[Aurelian]

^ Thanks.

Q - An analysis is carried out on a sample of unknown gas. The density of the gas is 2.86g/L at STP. The molecular formula of the gas is:
A) HCl
B) Cl2
C) NO2
D) SO2

Consider 1 litre of the unknown gas; m(gas) = 2.86g/L * 1L = 2.86g

Now, since gas amount does not depend on the identity of the gas, and we know the gas is evolved at STP, we can find out the amount of gas contained within 1L using molar volume calculations;

n(gas) = 1L/22.4Lmol-1 = 0.0446mol

That is, 0.0446 mol of gas, equates to 2.86g by mass.

Therefore, M(gas) = 2.86g/0.0446mol = 64.1gmol-1

Now, M(SO2) = 32.1gmol-1 + 32.0gmol-1 = 64.1gmol-1

Thus the gas must be SO2.

[mr.politiks]

Q - When drawing structural formulas of organic compounds (eg propene) can you draw all bonds at right angles or does it have to be correct (eg propene has a planar shape due to double bond...)

Q - How do we name/what VCAA wants? Eg - aminoethane or ethanamine

For second question, you MUST use the second as as amine group is only group present. If only one group is present, it is shown in suffix according to IUPAC. If more than one groups were present, the higher precedence group takes suffix and lower precedence group takes prefix. E.g: CH3-CH(OH)(NH2) has both amine and hydroxyl. Hydroxyl has higher precedence, so it takes suffix, and amine takes prefix therefore 1-aminoethan-1-ol. If we had CH2(OH)-CH2(NH2) then the higher precedence group (hydroxyl) has carbon number 1 (IUPAC assigns smallest C number to highest precedence group) and amine has c number 2. Therefore, it is 2-aminoethan-1-ol.
Check wikipedia IUPAC systematic nomenclature for organic compounds for rules and precedences. VCAA is tighter on this than most assume.

Other pointers: If numbers and necessary, they MUST not be used.
                         Don't refer to bond b/w two amino acids as a peptide bond. IN chem, it is an AMIDE bond.