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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: andy456 on June 06, 2010, 12:12:24 pm

Title: Questions
Post by: andy456 on June 06, 2010, 12:12:24 pm: If anyone could help me understand these I will be very appreciative.

-A sample of commercial ammonia has a label claim of 5.0% w/v concentration of NH4OH. This concentration cannot be expressed as:
A. 1.4 $molL^\(-1$
B. 5.0 x 10^4 $mgL^\(-1$
C. 50 $gL^\(-1$
D. 5.0 x 10^3 $gmL^\(-1$

-Myristic acid is a fatty acid. It can be described as
A. polar and saturated
B. polar and unsaturated
C. non-polar and saturated
D. non-polar and unsaturated
For this one I get that it is saturated, but I chose A because I thought that the carboxyl functional group causes the molecule to be polar.

- The number of phosphate groups in a DNA sample
A. equals the number of purine bases
B. equals the number of nitrogenous bases
C. is twice the number of nitrogenous bases
D. is twice the number of pentose sugar molecules
Title: Re: Questions
Post by: crayolé on June 06, 2010, 12:31:02 pm: For the first one, All of them equal the same (1.4mol of NH4 is 50g) except D which is 5000g per L. It's asking you to find the actual value not the unit it is measuring with.

If you look in the log book and draw out Myristic acid you will find that there are no double bonds (saturated), alternatively you can get the molecular formula (C₁₄H₂₈O₂) of the acid into use the rule C_nH_2n to find out if its saturated or not.
If the number H's is less than double the number C's then its unsaturated ;]
Also, all fatty acids will be non polar because of the long strand of its non-polar hydrocarbon

In one nucelotide there will always be one phosphate, one nitrogenous base and one deoxyribose sugar. When these join together to make DNA they well always be equal as there is one of each in a nucleotide.