Water, pH and Macromolecules

Q1: A Bronsted acid becomes __________ upon losing a proton.

A highly reactive

B its conjugate acid

C its conjugate base

D a hydronium ion

ANS:C - its conjugate base

No answer description is available. 

Q2: A compound that is capable of forming hydrogen bonds with water

A is probably held together by noncovalent bonds

B contains at least some polar covalent bonds

C should act as a good buffer for acids and bases

D does not dissolve well in water

ANS:B - contains at least some polar covalent bonds

No answer description is available. 

Q3: The dissociation constant of H2O at 25° C is

A 10-14 M

B 1014 M

C 10-7 M

D 107 M

ANS:A - 10-14 M

The dissociation constant is the degree of dissociation of the ions of a molecule. In this case: H+ and OH-.

The Pure water is completely ionized. therefore, has a neutral pH. pH = -log[H+]
7 = -log [H+] therefore, [H+] = 10^-7M.

Q4: Which of the following indicates that the pK of an acid is numerically equal to the pH of the solution when the molar concentration of the acid and its conjugate base are equal?

A Michaelis-Menten equation

B Haldanes equation

C Henderson-Hasselbalch equation

D Hardy-Windberg law

ANS:C - Henderson-Hasselbalch equation

No answer description is available. 

Q5: Which of the following acid/base pairs act as natural buffers in living systems?

A H2CO3/HCO3-

B H2PO4-/HPO42-

C Histidine+/histidine

D All of these

ANS:D - All of these

No answer description is available. 

Q6: If protein is made exclusively from nonpolar amino acids, then it will this protein interact with water?

A be repelled by water

B It will be attracted to water

C It will form a membrane in water

D It will act as a buffer and stabilize the pH

ANS:A - be repelled by water

No answer description is available. 

Q7: Weak acids generally have pKa

A values less than 1

B pKa values greater than 2

C been seldom found in living systems

D that cannot be used to buffer

ANS:B - pKa values greater than 2

No answer description is available. 

Q8: Which of the following character does not apply to water?

A The water molecule is asymmetric

B The water molecule readily forms hydrophobic interactions

C The covalent bonds in water are highly polarized

D All three atoms in the water molecule readily form hydrogen bonds

ANS:B - The water molecule readily forms hydrophobic interactions

Non-polar solute dissolve partially in Water thus, water form a cage around the solute this structure is called clathrate.

Q9: Salt dissolves well in water as water molecules

A form hydrogen bonds with the positively and negatively charged ions

B make nonpolar covalent bonds with the positively charged ions only

C surround the ions because of their charge but do not form hydrogen bonds

D share electrons with the ions to make polar covalent bonds

ANS:C - surround the ions because of their charge but do not form hydrogen bonds

No answer description is available. 

Q10: The reactions of molecules

A are the reactions of the functional groups

B are independent of the functional groups

C require an enzyme in all cases

D all of the above

ANS:A - are the reactions of the functional groups

No answer description is available. 

Q11: The reason that fats contain more energy than simple sugars, is fats have many more

A carbon atoms

B hydrogen atoms

C covalent bonds

D hydrogen bonds

ANS:C - covalent bonds

No answer description is available. 

Q12: Buffer solutions

A will always have a pH of 7

B are rarely found in living systems

C cause a decrease in pH when acids are added to them.

D tend to maintain a relatively constant pH.

ANS:D - tend to maintain a relatively constant pH.

No answer description is available. 

Q13: The main difference between an acid and a base is that

A bases are polar molecules and acids are not

B acids are polar molecules and bases are not

C bases donate hydrogen ions in water while acids accept hydrogen ions

D acids donate hydrogen ions in water while bases accept hydrogen ions

ANS:D - acids donate hydrogen ions in water while bases accept hydrogen ions

No answer description is available. 

Q14: The pH of a solution is determined by

A concentration of salt

B relative concentration of acids and bases

C dielectric constant of the medium

D environmental effect

ANS:B - relative concentration of acids and bases

No answer description is available. 

Q15: Which of the following will easily dissolve in a polar solvent?

A gasoline (heptanes & octanes)

B methane

C argon

D sodium chloride

ANS:D - sodium chloride

Polar solvents only discovered polar and ionic compounds, Al hydrocarbons (eg methane, Vaseline) are non-polar and only dissolved on polar and no ionic compounds.

Q16: Which of the following statements about water is correct?

A It is critical for many of the chemical processes found in living systems

B Polar substances that can form hydrogen bonds will dissolve in it

C Nonpolar substances like oils are not soluble in it

D All of the above

ANS:D - All of the above

Because water is neutral.

Q17: The strength of an acid depends on

A number of neutrons gain

B electronegativity

C number of double bonds

D number of protons released

ANS:B - electronegativity

No answer description is available. 

Q18: Which of the following organic groups are found in naturally occuring amino acids?

A Guanidinium ion

B Indole

C Imidazole

D All of these

ANS:D - All of these

No answer description is available. 

Q19: Polyprotic acids such as H3PO4, can act as acid-base buffers

A only in combination with polyprotic bases

B if their concentration is kept low

C at pH values around neutrality

D at pH values around any of their pKa's

ANS:D - at pH values around any of their pKa's

No answer description is available. 

Q20: Most of the important functional groups in biological molecules contain

A oxygen and/or nitrogen and are acidic

B oxygen and a phosphate

C nitrogen and a phosphate

D oxygen and/or nitrogen and are polar

ANS:D - oxygen and/or nitrogen and are polar

No answer description is available. 

Q21: Which of the following statements about covalently bonded molecules is false?

A Electrons are shared between the atoms that make up the molecule

B Noncovalent bonds may also be present, especially if the molecule is large

C Such molecules often result from the interaction of ionized atoms

D The chemical bonds that hold the molecule together are relatively strong

ANS:C - Such molecules often result from the interaction of ionized atoms

No answer description is available. 

Q22: Molecules in which the atoms are held together by __________ bonds have the strongest chemical linkages.

A noncovalent

B covalent

C ionic

D hydrogen

ANS:B - covalent

No answer description is available. 

Q23: A solution with pH = 5 is __________ than a solution with pH = 7.

A 2 times more basic

B 10 times more basic

C 10 times more acidic

D 100 times more acidic

ANS:D - 100 times more acidic

No answer description is available. 

Q24: Hydrogen bonds and hydrophilic interactions are types of

A weak chemical bonds that hold together the atoms within a molecule

B strong chemical bonds that hold together the atoms within a molecule

C weak chemical bonds that link together separate molecules

D strong chemical bonds that link together separate molecules

ANS:C - weak chemical bonds that link together separate molecules

No answer description is available. 

Q25: Who discovered and described the blood groups (ABO) classification?

A Theodor Kocher

B Karl Landsteiner

C Otto Warburg

D Karl Hooper

ANS:B - Karl Landsteiner

No answer description is available. 

Q26: The elements oxygen, nitrogen, and carbon

A can all form covalent bonds with other elements

B contain protons and neutrons in their atomic nuclei

C are common elements in the molecules that make up living organisms

D All of the above

ANS:D - All of the above

How oxygen and nitrogen and carbon form covelent bond with other molecular?

Q27: The lone pair electrons on oxygen in a H20 molecule

A carry a partial positive charge

B are not important for the properties of water

C carry a partial negative charge

D form covalent bonds in ice

ANS:C - carry a partial negative charge

No answer description is available. 

Q28: Which of the following alcohols would be most soluble in water?

A methanol

B ethanol

C butanol

D octanol

ANS:A - methanol

No answer description is available. 

Q29: What is the concentration, in moles/liter, of the hydrogen ion, if pH of a solution is 7?

A 7

B 7 x 10-7

C 5 x 10-7

D 1 x 10-7

ANS:D - 1 x 10-7

No answer description is available. 

Q30: A biological polymer contains alanine, tyrosine, and lysine. Which of the following will be true about this molecule?

A DNA

B Strong base

C Phospholipid

D Protein

ANS:D - Protein

No answer description is available. 

Q31: The effectiveness or capacity of a buffer solution can be affected by

A molar concentration of the buffer components

B concentration of the conjugate base to the weak acid

C both (a) and (b)

D temperature of buffer components

ANS:C - both (a) and (b)

No answer description is available. 

Q32: H2O and CH4 are both examples of

A molecules

B ions

C acids

D none of these

ANS:A - molecules

No answer description is available. 



img not found
img

For help Students Orientation
Mcqs Questions

One stop destination for examination, preparation, recruitment, and more. Specially designed online test to solve all your preparation worries. Go wherever you want to and practice whenever you want, using the online test platform.