KAPLAN DIAGNOSTIC CHEM/PHYS
QUESTIONS WITH CORRECT
ANSWER.
1. WHICH ENERGY VALUES IN FIGURE 1 COULD BE ALTERED BY THE INTRODUCTION OF A CATALYST?
RIGHT ANSWER REASON: IN FIGURE 1 IT SHOWS THE TWO STEP MECHANISM AND TWO Ea'S so adding a
catalyst would only affect activation energy by lowering it and increasing the rate of reaction.
2. which of the following cannot be the mechanism for the rate determining step of this reaction?
wrong answer reason: I was thinking that a molecule of B cannot react with another molecule of B
Because they're technically the same molecule.
correct answer: 2 molecules of A collide with a molecule of B is wrong because a reaction with second
order kinetics can only involve 2 reactants. in this case there are three reactants.
3. From the information provided in the passage, which of the following is necessarily true.
correct answer reason: Keq is greater than 1 because in the passage it stated that the run is
spontaneous which means it has G<0 , thus making Keq>1
4.Ozone has a high oxidation potential, and will readily decompose urea: (NH2)2CO + O3 --> N2 + CO2
+2H2O. In this reaction, what is the oxidation number of carbon as a reactant and product, respectively?
correct answer reason: I guessed on this question and spent more than a minute. simple explanation is
that nitrogen has an oxidation number of +3 and there are 2 nitrogens so the total is +6, Hydrogen has
the oxidation number of +1, and there 4 hydrogen so it makes it +4, the oxidation number for Oxygen is
-2 so its total -4 but urea is neutral so the carbon oxidation number should be +4.
5. How many grams of AlCl3 are produced when 3 grams of Al(OH)2 react completely with excess HCl?
,correct answer reason: performed the dimensional analysis. the question stem tells us that HCl is in
excess which means that Al(OH)3 is the limiting reagent and all of 3 grams of Al(OH)3 will be consumed.
3g Al(OH)3 x 1 mol Al(OH)3/ 78 g Al(OH)3= 1/26 mole Al(OH)3
1/26 mole AlCl3 x 133.5 g/ 1 mole AlCl3 = 5.05 g
6. If HCl is the only substance present in the stomach, what is the pH?
correct answer reason: since the question is talking about H+ ions I thought it would be the equation
pH= -log(H+)
in the first paragraph it states that human stomach contains 0.15 N HCl in people with sensitive
stomachs.
"N" means in context of acids which is equal to 0.15 moles of H+ per liter, meaning that H+ = 0.15 M. So,
pH= -log(0.15)
7. while the active ingredients in most antacids are soluble in the acidic environment of the stomach,
their solubility is significantly reduced in pure water. if a very finely ground powder of one such
compound (CaCO3, for example), is mixed in 1:5 ratio by mass with deionized water, which of the
following is most likely true?
wrong answer reason: I thought if its soluble then excess would be soluble too making it a homozygous
mixture. I thought it was colloidal making it cloudy.
actual explanation: the question stem tells us that CaCO3 is not very soluble in pure water so only a
small amount will dissociate into Ca2+ and CO3 2-. Most of the powder will remain undissolved but
because it is " finely ground" the particles will become suspended. such a heterozygous mixture is
known as colloid.
Based on this only II is correct. Because a small amount of solution will dissociate, III can be eliminated,
the solution will be electrolytic.
, 8. Strong, soluble bases such as alkaline earth metal hydroxides are not used as antacids, but are often
used in laboratory titrations. what volume of an aqueous 1.5 M Ba(OH)2 solution would be required to
neutralize 10 mL of stomach acid.
wrong answer reason: I guessed on this did not use the right formulation.
correct answer explanation: for neutralization to occur H+ should equal OH-. 0.15 N HCl corresponds to
0.15 M HCl. The number of moles of H+ contained in 10 mL of stomach acid is therefore:
0.15 mol/L x 0.010 L= 1.5 x10^-3 mol.
2 moles of OH = 3.0 N
so 1.5/3.0 = 0.5 mL
9. which of the following is the empirical formula of a compound containing 23g of sodium, 16 g of sulfur
and 32 g of Oxygen.
wrong answer reason: divided all these masses by their corresponding molecular weights.
correct answer explanation:
first step is to convert grams into moles.
the molar masses for sodium, sulfur, and oxygen are 23, 32, and 16 respectively.
sodium: 23/23= 1 mole
sulfur: 16/32 = 0.5 moles
oxygen: 32/16= 2 moles
*non whole number such as 0.5 are not used when writing the empirical formula.
in the second step of the calculation, everything must be multiplied by the smallest value that yields a
whole number of moles for all three elements.
so it should be multiplied by 2 which will give Na2SO4
which of the following best explains why 1-chloropentane and 1-pentanol can be separated by fractional
distillation?
QUESTIONS WITH CORRECT
ANSWER.
1. WHICH ENERGY VALUES IN FIGURE 1 COULD BE ALTERED BY THE INTRODUCTION OF A CATALYST?
RIGHT ANSWER REASON: IN FIGURE 1 IT SHOWS THE TWO STEP MECHANISM AND TWO Ea'S so adding a
catalyst would only affect activation energy by lowering it and increasing the rate of reaction.
2. which of the following cannot be the mechanism for the rate determining step of this reaction?
wrong answer reason: I was thinking that a molecule of B cannot react with another molecule of B
Because they're technically the same molecule.
correct answer: 2 molecules of A collide with a molecule of B is wrong because a reaction with second
order kinetics can only involve 2 reactants. in this case there are three reactants.
3. From the information provided in the passage, which of the following is necessarily true.
correct answer reason: Keq is greater than 1 because in the passage it stated that the run is
spontaneous which means it has G<0 , thus making Keq>1
4.Ozone has a high oxidation potential, and will readily decompose urea: (NH2)2CO + O3 --> N2 + CO2
+2H2O. In this reaction, what is the oxidation number of carbon as a reactant and product, respectively?
correct answer reason: I guessed on this question and spent more than a minute. simple explanation is
that nitrogen has an oxidation number of +3 and there are 2 nitrogens so the total is +6, Hydrogen has
the oxidation number of +1, and there 4 hydrogen so it makes it +4, the oxidation number for Oxygen is
-2 so its total -4 but urea is neutral so the carbon oxidation number should be +4.
5. How many grams of AlCl3 are produced when 3 grams of Al(OH)2 react completely with excess HCl?
,correct answer reason: performed the dimensional analysis. the question stem tells us that HCl is in
excess which means that Al(OH)3 is the limiting reagent and all of 3 grams of Al(OH)3 will be consumed.
3g Al(OH)3 x 1 mol Al(OH)3/ 78 g Al(OH)3= 1/26 mole Al(OH)3
1/26 mole AlCl3 x 133.5 g/ 1 mole AlCl3 = 5.05 g
6. If HCl is the only substance present in the stomach, what is the pH?
correct answer reason: since the question is talking about H+ ions I thought it would be the equation
pH= -log(H+)
in the first paragraph it states that human stomach contains 0.15 N HCl in people with sensitive
stomachs.
"N" means in context of acids which is equal to 0.15 moles of H+ per liter, meaning that H+ = 0.15 M. So,
pH= -log(0.15)
7. while the active ingredients in most antacids are soluble in the acidic environment of the stomach,
their solubility is significantly reduced in pure water. if a very finely ground powder of one such
compound (CaCO3, for example), is mixed in 1:5 ratio by mass with deionized water, which of the
following is most likely true?
wrong answer reason: I thought if its soluble then excess would be soluble too making it a homozygous
mixture. I thought it was colloidal making it cloudy.
actual explanation: the question stem tells us that CaCO3 is not very soluble in pure water so only a
small amount will dissociate into Ca2+ and CO3 2-. Most of the powder will remain undissolved but
because it is " finely ground" the particles will become suspended. such a heterozygous mixture is
known as colloid.
Based on this only II is correct. Because a small amount of solution will dissociate, III can be eliminated,
the solution will be electrolytic.
, 8. Strong, soluble bases such as alkaline earth metal hydroxides are not used as antacids, but are often
used in laboratory titrations. what volume of an aqueous 1.5 M Ba(OH)2 solution would be required to
neutralize 10 mL of stomach acid.
wrong answer reason: I guessed on this did not use the right formulation.
correct answer explanation: for neutralization to occur H+ should equal OH-. 0.15 N HCl corresponds to
0.15 M HCl. The number of moles of H+ contained in 10 mL of stomach acid is therefore:
0.15 mol/L x 0.010 L= 1.5 x10^-3 mol.
2 moles of OH = 3.0 N
so 1.5/3.0 = 0.5 mL
9. which of the following is the empirical formula of a compound containing 23g of sodium, 16 g of sulfur
and 32 g of Oxygen.
wrong answer reason: divided all these masses by their corresponding molecular weights.
correct answer explanation:
first step is to convert grams into moles.
the molar masses for sodium, sulfur, and oxygen are 23, 32, and 16 respectively.
sodium: 23/23= 1 mole
sulfur: 16/32 = 0.5 moles
oxygen: 32/16= 2 moles
*non whole number such as 0.5 are not used when writing the empirical formula.
in the second step of the calculation, everything must be multiplied by the smallest value that yields a
whole number of moles for all three elements.
so it should be multiplied by 2 which will give Na2SO4
which of the following best explains why 1-chloropentane and 1-pentanol can be separated by fractional
distillation?
