help; i really need a tutor

[khalil]

When talking about standard solutions, how does having a high molar mass minimise errors?

[Mao]

the standard has a known weight, but the importance of this is that you know the number of moles from that weight.

If the standard has a low molar mass, the errors of measurement in weight could mean a huge variation in the number of moles. However, if it had a higher molar mass, the errors of measurement would correspond to a significantly lower variation in the number of moles, hence more accurate.

Think about how accurately you can calculate:
1) how many grains of rice in 1kg bag
2) how many chocolate bars in 1kg bag

[khalil]

A 0.360 g sample of an organic compound containing carbon, hydrogen and oxygen was burnt in excess oxygen. When the gases evolved were passed through anhydrous CaCl2 its mass increased by 0.216 g. The remaining gases, when bubbled through a NaOH solution, increased its mass by 0.528 g. The mass of oxygen in the sample is ...

[khalil]

(c)    Explain how the primary structure of DNA is responsible for the primary structure of a protein.

[d0minicz]

primary structure of DNA is the specific sequence of BASES ; which carries the genetic code => for specific amino acids => specific protein primary structure (sequence of amino acids)

[TrueTears]

Extension: 3 base pairs (a codon) codes for 1 amino acid

[khalil]

In the mass spectrum of aspirin, there is a peak at 138. What part of aspirin would this peak be responsible for? I mean if it was for salicyclic acid, then wouldnt it be 137?

[Mao]

Is it a large peak or small peak?

If it is a small peak, it may because of one C13 (isotope of carbon that has a mass of 13) is present in it.

[khalil]

Its large, its labelled so im guessing its significant

[Mao]

Salicylic acid's molecular weight is 138.

[khalil]

yer but its not in its full form in aspirin, its H is missing

[khalil]

Also, are disaccharides solid? How can you tell. There was a VCAA question on this

[khalil]

VCAA says that Q5aiii is glucose...is this true?
http://www.vcaa.vic.edu.au/vce/studies/chemistry/assessreports/2005/chemistryassessreportnov05.pdf

[Mao]

yer but its not in its full form in aspirin, its H is missing

An H. radical may join on to the m/e=137 ion. It is possible

Also, are disaccharides solid? How can you tell. There was a VCAA question on this

table sugar is a disaccharide

[khalil]

more energy is required to vibrate:
a) C-C compared to C=C            b) C-Cl compared to C-Br            c) C-O compared to C-H           d)C=C compared to C=-C (triple bond)