Discussion on molarity and osmolarity help

Discussion on molarity and osmolarity help
29. If the following amounts of the given substances were dissolved in water, which
would result in four osmoles of dissolved particles?
A. 2 mol of C6H12O6
B. 2 mol of Na Cl−
C. 2 mol of C12H22O11
D. 2 mol of (Na )2SO4
2−
Answer is B: Osmole is a term used when the solute particles came from an ionic
substance. Osmoles = moles × number of ions in formula. There are two ions in the
formula for sodium chloride, hence 4 osmoles. There are three ions in the formula
for sodium sulphate, hence 6 osmoles.
30. What is the difference between “molarity” and “osmolarity”?
A. Molarity applies only to covalent compounds, while osmolarity applies
only to ionic compounds.
B. Osmolarity is molarity multiplied by two.
C. The molarity and osmolarity of a solution are the same for dissolved ionic
compounds but are different for dissolved covalent compounds.
D. Osmolarity refers to the concentration of dissolved particles in a solution
which may not be the same as the number of moles of substance that was
dissolved per litre of solution.
Answer is D: Choice D is better than choice A as molarity can also be applied to
ionic compounds.
31. Human blood has an osmolarity that lies within the range 280–
300 mosmol/L. Which of the following statements is correct?
A. An isotonic solution has osmolarity that is either less than 280 or greater
than 300 mosmol/L.
B. A hypotonic solution has osmolarity between 280 and 300 mosmol/L.
C. A hypertonic solution has osmolarity between 280 and 300 mosmol/L.
D. An isotonic solution has osmolarity between 280 and 300 mosmol/L.
Answer is D: An isotonic solution has the same osmolarity as blood.
32. What distinguishes an osmole from a mole?
A. In a sample of substance, the number of osmoles is twice the number of
moles.
B. Both mole and osmole may be used in reference to ionic compounds, while
covalent compounds are described by mole alone.
C. The mass of a mole is the sum of the relative atomic masses (RAM) of the
atoms in the formula stated as grams. An osmole is half of this mass.
D. An osmole applies only to covalent molecular substances, whereas a mole
is validly applied to both covalent and ionic substances