Lecture 2 - Aqueous solutions Flashcards
Which of the following statements about water, H2O, is CORRECT?
(A) Liquid water is a poor solvent for polar molecules.
(B) Water molecules in ice are held together by hydrogen bonds.
(C) A water molecule solvating a cation has its H atoms lying closer to the cation
than its O atom.
(D) If a compound dissolves in water it must be a strong electrolyte.
(B) Water molecules in ice are held together by hydrogen bonds.
In ice, water molecules arrange themselves in a crystal lattice structure, where each water molecule forms hydrogen bonds with neighbouring water molecules. This arrangement stabilises the solid structure of ice.
Which of the following best represents the equation for the dissolution of lead (II)
carbonate (PbCO3), a poorly soluble compound?
A)PbCO3 (s) + H2O(l) ⇌ Pb2+(aq) + CO3-(aq)
B) PbCO3(s) + H2O(l) –> Pb2+(aq) + CO3-(aq)
C) PbCO3(s) ⇌ Pb2+(aq) + CO3-(aq)
D)It is not possible to write an equation for this process because PbCO3 is poorly soluble.
C) PbCO3(s) ⇌ Pb2+(aq) + CO3-(aq)
⇌ means the reaction is significant in both directions
Which of the following statements regarding the dissolution of lead(II) carbonate (PbCO3) (a poorly soluble compound) is INCORRECT?
A) The lead cations in solution are surrounded by water molecules with the oxygen atoms nearest to them.
B) The solid does not dissolve completely unless a large excess of water is used.
C) The chloride anions are surrounded by water molecules with the hydrogen atoms closest to
them.
D) Poorly soluble ionic compounds are classed as strong electrolytes because they produce
ions in solution
D) Poorly soluble ionic compounds are classed as strong electrolytes because they produce
ions in solution
Which of the following statements about water H2O is INCORRECT?
(A) Solvation of an ionic solid involves interactions of charged ions with the dipoles of H2O molecules.
(B) N2(g) is slightly soluble in H2O because N2 is an electronegative element.
(C) H2O molecules solvating a cation have their O atoms lying closer to the cation than their H atoms.
(D) Liquid water is a good solvent for polar molecules.
B) N2(g) is slightly soluble in H2O because N2 is an electronegative element.
Nitrogen gas (N2) is not soluble in water because it is a nonpolar molecule composed of two nitrogen atoms held together by a strong triple bond. Water, being a polar molecule, does not interact strongly with nonpolar molecules like N2. Therefore, N2 is not soluble in water.
Which of the following statements about water H2O is INCORRECT?
(A) Polar molecules must always dissociate to some extent to dissolve in water.
(B) Cl2(g) is slightly soluble in H2O because the electron cloud surrounding Cl2 is able to be polarised by H2O.
(C) H2O molecules solvating an anion have their H atoms lying closer to the anion than their O atoms.
(D) Strong electrolytes are completely dissociated in solutions where water is the
solvent.
(A) Polar molecules must always dissociate to some extent to dissolve in water.
Polar molecules do not always have to dissociate to some extent to dissolve in water. Dissolving in water involves the interactions between the polar molecules and the water molecules, typically through hydrogen bonding or dipole-dipole interactions. Some polar molecules may undergo dissociation when dissolved in water, but others may remain intact and simply form solvation shells with water molecules around them.
T or F
Electrolyte solutions conduct electricity due to electrons moving in solution
False
Electrolyte solutions conduct electricity due to ION movement
T or F
If you add a nonelectrolyte to an aqueous solution that already contains an electrolyte, the electrical conductivity will not change
True
Many ionic solids disolve in water as strong electrolytes (separated ions in a solution). Which of the following is the most correct:
A. Water is a strong acid and therefore is good at dissolving ionic solutions
B. Water is good at solvating ions because the hydrogen and oxygen atoms in water molecules bear partial charges
C. The hydrogen and oxygen bonds of water are easily broken by ionic solids
B. Water is good at solvating ions because the hydrogen and oxygen atoms in water molecules bear partial charges
Define electrolyte
Substance whose aqueous solution contains ions
Define nonelectrolyte
Substance that does not form ions in aqueous solutions
Ionic solids, acids and bases are all…(electrolytes or non electrolytes)
Electrolytes
Which of the following statements is CORRECT?
(A) When water freezes, the molecules try to maximise the number of hydrogen bonds between them, causing the ice to have a lower density than liquid water.
(B) When water freezes, the molecules try to minimise the number of hydrogen bonds between them, causing the ice to have a lower density than liquid water.
(C) When water freezes, the molecules try to maximise the number of hydrogen bonds between them, causing the ice to have a higher density than liquid water.
(D) When water freezes, the molecules try to minimise the number of hydrogen bonds between them, causing the ice to have a higher density than liquid water.
(A) When water freezes, the molecules try to maximise the number of hydrogen bonds between them, causing the ice to have a lower density than liquid water.
