last few questions..

[messenger]

hi everyone, just a few questions....

1. how do you know if or how a reaction will go to completion, like this one:
The reaction of AgNO3 and Na2SO4 goes to completion b/c...?

2. whats more soluble in water:
a salt, or OH containing compound...and the answer was salt in the example i had! i thought like dissolves like, and that COOH or an OH molecule is more soluble...?

3. which is a meso compound...trans isomer or cis isomer?

thanks for the help!
messenger.

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[Pilot Mike]

hi everyone, just a few questions....

1. how do you know if or how a reaction will go to completion, like this one:
The reaction of AgNO3 and Na2SO4 goes to completion b/c...?

2. whats more soluble in water:
a salt, or OH containing compound...and the answer was salt in the example i had! i thought like dissolves like, and that COOH or an OH molecule is more soluble...?

3. which is a meso compound...trans isomer or cis isomer?

thanks for the help!
messenger.

1. Remember your solubility rules.
I. Grp1 and NH4+ salts are soluble
II. N03-, C2H3O2-, and ClO4 - are soluble
III. Ag, Pb, Hg (the ones whos name isn't the same) are insoluble unless with # II.

So for this one, AgNO3 will precipitate with this reaction.

2. I don't know the example you had, but go by the solubility rules. F = q1q2/r^2 also relates to solubility.

3. Again, not sure exactly the question you saw. Meso compounds have an internal plane of symmetry, and chiral centers that do not rotate plane polarized light. One way I've seen is if an alekene is originally trans and you have an addition to it, it would go cis, which could be meso depending on whats else is on the other carbons. if its cis and you do an addition, the product would be trans.
like if you have 1,2-dibromopentene (ring structure) and you add H2/Pt, it will add as a syn addition, it will be cis config and a meso compound.

i hope thats right...at least thats how i remembered it

 

[messenger]

1. Remember your solubility rules.
I. Grp1 and NH4+ salts are soluble
II. N03-, C2H3O2-, and ClO4 - are soluble
III. Ag, Pb, Hg (the ones whos name isn't the same) are insoluble unless with # II.

So for this one, AgNO3 will precipitate with this reaction.

2. I don't know the example you had, but go by the solubility rules. F = q1q2/r^2 also relates to solubility.

3. Again, not sure exactly the question you saw. Meso compounds have an internal plane of symmetry, and chiral centers that do not rotate plane polarized light. One way I've seen is if an alekene is originally trans and you have an addition to it, it would go cis, which could be meso depending on whats else is on the other carbons. if its cis and you do an addition, the product would be trans.
like if you have 1,2-dibromopentene (ring structure) and you add H2/Pt, it will add as a syn addition, it will be cis config and a meso compound.

i hope thats right...at least thats how i remembered it

great, so how do you know if something precipitates?
and for the last one, so would a cis butene be meso, or trans butene?
i am getting these confused when they arent in a fisher projection and drawn out normally? b/c of course i can tell what a meso is in fischer projection, but not normal?
thanks for your tips!
messenger.

 

[messenger]

are there questions like this on dat...and could i ask for help on this one?

In a plant, blue petal (B) is dominant to white petal (b); and long stem (L) is dominant to short stem (l). Determine the parental genotypes if 299 blue petal long stem, 302 blue petal short stem, 103 white petal long stem, and 98 white petal short stem plants are produced.
A. BbLl x Bbll
B. BbLl x BbLl
C. BBll x BbLl
D. Bbll x bbLl
E. bbLl x bbLl

also, how do you do dihybrid crosses in general? thank you.
messenger.

 

[SgtSadhu]

great, so how do you know if something precipitates?
and for the last one, so would a cis butene be meso, or trans butene?
i am getting these confused when they arent in a fisher projection and drawn out normally? b/c of course i can tell what a meso is in fischer projection, but not normal?
thanks for your tips!
messenger.

if its insoluble it precipitates

if you have a butene you have geometrical isomers and so itd be E or Z

Meso, Enantiomers, and Diasteriomers have to do with chirality. An chiral molecule will have 4 diff substituents so a butene can't be a meso.

 

[DMD to Be]

are there questions like this on dat...and could i ask for help on this one?

In a plant, blue petal (B) is dominant to white petal (b); and long stem (L) is dominant to short stem (l). Determine the parental genotypes if 299 blue petal long stem, 302 blue petal short stem, 103 white petal long stem, and 98 white petal short stem plants are produced.
A. BbLl x Bbll
B. BbLl x BbLl
C. BBll x BbLl
D. Bbll x bbLl
E. bbLl x bbLl

also, how do you do dihybrid crosses in general? thank you.
messenger.

First, I scan the information and see that there is an obvious 3:3:1:1 ratio. That eliminates answer choice E, b/c two pair of recessive traits will give only recessive, and there are dominant blue petals in the offspring. It also eliminates choice C b/c BBxBb gives only the dominant blue. Then, I see there is a significantly greater number of blue petal offspring(299+302 = about 600) compared to white petal (103+98 = about 200). This gives a 3:1 ratio of blue:white. This eliminates choice D, b/c Bbxbb gives a 1:1 ratio, and you need a 3:1. The only remaining choices are A and B. This is where you must take a look at long stem vs. short stem. In the offspring there are about 400 long stem and there are about 400 short stem. Got it! That's a 1:1 ratio. Knowing that, A must be the correct answer b/c Ll x ll gives a 1:1 ratio. This problem does involve a little reasoning... Actually, not really if you've had genetics where you pretty much learn the patterns and can spot the answer in several seconds. Just thought I'd elaborate the reasoning behind the correct answer....