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# Tutor profile: Alex F.

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Alex F.
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## Questions

### Subject:Organic Chemistry

TutorMe
Question:

Predict the product of CH3CH2Br with H3PO4 and heat.

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Alex F.

A nonnucleophilic acid like H3PO4 is a clear indicator of an E1 reaction, especially in the presence of heat so the product would have a double bond. First, since it is an E1 reaction, like an SN1 reaction, first the leaving group leaves. This puts a carbocation on the carbon that had the leaving group since this is unstable one of the hydrogens from the other carbon is taken by the conjugate base of the acid. Next, the carbon shares its electrons with the carbon with the carbonation, making a double bond. The product will be C2H4.

### Subject:Chemistry

TutorMe
Question:

What is the change in pH when 20.0 ML of 0.06M NaOH is added to 50.0 mL of citric acid that is both 0.1M acid and conjugate base? Pka= 3.13. Assume monoprotic.

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Alex F.

To find the pH of a buffer solution you use the Henderson-Hasselbach equation: pH= pKa+ log [A-]/[HA]. So in this case since we are adding base the base concentration will increase and the acid will decrease since it is reacting with the base. Also since liquid is being added the volume changes so for the base concentration the equation is: [0.050L*0.1M + 0.020L*0.06M]/0.050mL +0.020mL = 0.08857M And for the acid concentration it would be [0.050L*0.1M - 0.020L*0.06M]/0.050mL +0.020mL = 0.0542857M Plugging into the equation we get, pH= 3.13+ log[0.08557/0.0542857]= 3.32768 ~ 3.33 so the change in pH would be about 0.20.

### Subject:Biology

TutorMe
Question:

Areas with high rates of Malaria tend to have a higher allele frequency for the recessive allele of sickle cell anemia. The alleles display dominance, which makes all the blood cells abnormally shaped if homozygous, but only some cells abnormally shaped if heterozygous. Thus, being homozygous recessive is often lethal whereas being heterozygous is viable. Why does a selective pressure towards abnormally shaped blood cells occur?

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Alex F.

Being heterozygous protects the individual from malaria by sacrificing some of the oxygen carrying capabilities of the blood cells. Individuals with homozygous dominant genes would be out-competed by heterozygous individuals in the population because malaria is more deadly in those areas than having partially misshaped blood cells. Also, since homozygous recessive is often nonviable, the selective pressure will favor heterozygous as the middle ground between death by lack of oxygen-carrying blood cells, and malaria, essentially protecting the individual from both.

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