2010 Destroyer Bio # 285 Mistake

[bigndog525]

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Consider a sample of DNA that undergoes four rounds of replication. What percent of the original-stranded DNA remains?

Destroyer says 12.5 % and Kaplan has the same question, but says 6.25 %. I believe Kaplan is correct.

100 -----> 50 ------> 25 -------> 12.5 -------> 6.25

Anyone know whats up?



ALSO, Can someone help me solve this problem....

It was found that 1.5 x 10^-6 moles of BaSO4 dissolves in 1 L of 0.001 M Na2SO4 solution. What is the solubility constant for BaSO4?

Correct Answer: (1.5 x 10^-6)(10^-3)

How did they come to this answer? Thanks.

 

[wired202808]

Consider a sample of DNA that undergoes four rounds of replication. What percent of the original-stranded DNA remains?

Destroyer says 12.5 % and Kaplan has the same question, but says 6.25 %. I believe Kaplan is correct.

100 -----> 50 ------> 25 -------> 12.5 -------> 6.25

Anyone know whats up?



ALSO, Can someone help me solve this problem....

It was found that 1.5 x 10^-6 moles of BaSO4 dissolves in 1 L of 0.001 M Na2SO4 solution. What is the solubility constant for BaSO4?

Correct Answer: (1.5 x 10^-6)(10^-3)

How did they come to this answer? Thanks.

i think it is a mistake, i remember you have to do 0.5^4 because its half of the original strand so it would be 6.25 remaining, but have others confirm this as well

 

[Bis-GMA111]

common ion effect:

you have to take the .001 M from Na2SO4 into account..

Ba2SO4-->Ba(+) + SO4 (2-)

Ksp=[Ba][SO4]

[1.5x10^-6][.001+x] here the x is negligible
[1.5x10^-6][.001]=Ksp

poorly written question IMO

 

[bigndog525]

i think it is a mistake, i remember you have to do 0.5^4 because its half of the original strand so it would be 6.25 remaining, but have others confirm this as well

exactly what I'm sayin

common ion effect:

you have to take the .001 M from Na2SO4 into account..

Ba2SO4-->Ba(+) + SO4 (2-)

Ksp=[Ba][SO4]

[1.5x10^-6][.001+x] here the x is negligible
[1.5x10^-6][.001]=Ksp

poorly written question IMO

Thank you very much!! wow that was easy.... I guess I just wasn't thinking clearly lol