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[Question #4]
[FONT=&quot]
By the way, these MCAT questions are for the American MCAT given in the US, not for medical colleges in other countries. The mcat exams in other countries are not at all similar to these practice questions.

Passage I[/FONT]

[FONT=&quot]
A series of chemical reactions was carried out to study the chemistry of lead. [/FONT]

[FONT=&quot]Reaction 1 [/FONT]
[FONT=&quot]Initially, 15.0 mL of 0.300 M Pb(NO3)2(aq) was mixed with 15.0 mL of 0.300 M Na2SO4(aq).All the Pb(NO3)2 reacted to form Compound A, a white precipitate.Compound A was removed by filtration. [/FONT]
[FONT=&quot]
Reaction 2 [/FONT]

[FONT=&quot]Next, 15.0 mL of 0.300 M KI(aq) was added to Compound A. The mixture was agitated and some of Compound A dissolved. In addition, a yellow precipitate of PbI2(s) was formed. [/FONT]
[FONT=&quot]
Reaction 3 [/FONT]

[FONT=&quot]The PbI2(s) was separated and mixed with 15.0 mL of 0.300 M Na2CO3(aq). A white precipitate of PbCO3(s) formed. All of the PbI2(s) was converted into PbCO3(s). [/FONT]
[FONT=&quot]
Reaction 4 [/FONT]

[FONT=&quot]The PbCO3(s) was removed by filtration and a small sample gave off a gas when treated with dilute HCl. [/FONT]
[FONT=&quot]
1. Which of the following reactions depicts the formation of the gas in Reaction 4?[/FONT]

[FONT=&quot]PbCO3(s) + 2 HCl(aq) = PbCl2(aq) + CO2(g) + H2O(l) [/FONT]
[FONT=&quot]Na2CO3(aq) + 2 HCl(aq) = 2 NaCl(aq) + CO2(g) + H2O(l) [/FONT]
[FONT=&quot]PbCO3(s) + 2 HCl(aq) = PbC2(s) + Cl2(g) + H2O(l) [/FONT]
[FONT=&quot]PbI 2(s) + HCl(aq) = PbCl2(aq) + HI(g) [/FONT]
[FONT=&quot]
2. The identity of Compound A is:[/FONT]
  1. [FONT=&quot]Pb(NO3)2. [/FONT]
  2. [FONT=&quot]PbI2. [/FONT]
  3. [FONT=&quot]NaNO3. [/FONT]
  4. [FONT=&quot]PbSO4. [/FONT]
3.[FONT=&quot] Pb(OH)2(s) is slightly soluble in water. How would the amount of Pb(OH)2(s) that normally dissolves in 1 L of water be affected if the pH were 9.0?[/FONT]
  1. [FONT=&quot]Less would dissolve. [/FONT]
  2. [FONT=&quot]The same amount would dissolve. [/FONT]
  3. [FONT=&quot]More would dissolve. [/FONT]
  4. [FONT=&quot]There is no way to predict the effect of the change in pH of the water. [/FONT]
4. [FONT=&quot]A soluble form of Pb2+can be carefully added to a solution tosequentially precipitate and separate anions present in the solution. When Pb2+is added, in what order will the following anions be precipitated?[/FONT]
  1. [FONT=&quot]SO42- then I- [/FONT]
  2. [FONT=&quot]CO32- then I- [/FONT]
  3. [FONT=&quot]SO42- then CO32- [/FONT]
  4. [FONT=&quot]I- then CO32- [/FONT]
5. [FONT=&quot]How many moles of Na+ ions are there in the initial Na2SO4(aq) solution used in Reaction 1?[/FONT]
  1. [FONT=&quot]0.0018 mole [/FONT]
  2. [FONT=&quot]0.009 mole [/FONT]
  3. [FONT=&quot]0.045 mole [/FONT]
  4. [FONT=&quot]0.090 mole[/FONT]
 

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whats the answer to question 4? my guess is

1) first reaction
2) 4
3) less would dissolve
4) 4
5) 3

can someone verify these
 

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For Question 4:
1 is PBCO3 (s) + 2 HCl = PbCl2 (aq) + CO2 (g) + H2O (l)
2 is PbSO4
3 More would dissolve (that's a guess I'm not entirely sure)
4. SO4 then I (not sure on this one either)
5. .045 moles
 

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[Question #1]

Which of the following is the mRNA start codon in most cases?

A. UAA
B. AGU
C. AUG
D. UGA

If you have an answer, please reply with [Answer #n] and as always, stay tuned for more questions 8)
ans is ( c) ,
because UGA and UAA are stop codons , AGU codes for serine while AUG codes for metheonine that is starting codon.:)
 

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The acidity of chyme stimulates
(a).pancreatic cell
(b).liver cell
(c).duodenal cell
(d).all

- - - Updated - - -

MAXIMUM NUMBER OF ENZYMES OCCUR IN
(A).OMNIVORES
(B).CARNIVORES
(C).OMNIVORES
(D).ALL HAVE SAME NUMBER

- - - Updated - - -

IF YOU HAVE AN ANSWER PLEASE RPLY

- - - Updated - - -

:)
 

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The acidity of chyme stimulates
(a).pancreatic cell
(b).liver cell
(c).duodenal cell
(d).all

- - - Updated - - -

MAXIMUM NUMBER OF ENZYMES OCCUR IN
(A).OMNIVORES
(B).CARNIVORES
(C).OMNIVORES
(D).ALL HAVE SAME NUMBER

- - - Updated - - -

IF YOU HAVE AN ANSWER PLEASE RPLY

- - - Updated - - -

:)
1.d
2.a
 

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as carnivores eat flesh of animals so they have maximum number of enzymes ...... predators usually eat live prey...to digest it they have more enzymes

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i m a bit confuse about it ........
 
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