Question

(a) ions in a certain volume of 0.20 m nacl(aq) are represented in the box above on the left. in the box above on the right, draw a particulate diagram that represents the ions in the same volume of 0.10 m cacl₂(aq). note on your ap exam, you will handwrite your responses to free - response questions in a test booklet (b) briefly explain how the presence of charged ions in ionic solids such as nacl(s) helps to explain why nacl(s) is soluble in water.

Explanation:

Step1: Analyze ion - concentrations in NaCl

In 0.20 M NaCl(aq), the concentration of Na⁺ ions is 0.20 M and the concentration of Cl⁻ ions is 0.20 M.

Step2: Analyze ion - concentrations in CaCl₂

In 0.10 M CaCl₂(aq), the concentration of Ca²⁺ ions is 0.10 M and the concentration of Cl⁻ ions is 0.20 M (since there are 2 moles of Cl⁻ for every 1 mole of CaCl₂). So, for the particulate diagram of CaCl₂, the number of Ca²⁺ ions should be half of the number of Na⁺ ions in the NaCl diagram, and the number of Cl⁻ ions should be the same as in the NaCl diagram.

Step3: Answer part (b)

Water is a polar molecule. The positive end of the water molecule (hydrogen - end) is attracted to the negatively - charged Cl⁻ ions in NaCl, and the negative end of the water molecule (oxygen - end) is attracted to the positively - charged Na⁺ ions. These ion - dipole attractions overcome the ionic bonds in NaCl(s), allowing it to dissolve in water.

Answer:

(a) For the particulate diagram of 0.10 M CaCl₂(aq), draw half as many Ca²⁺ ions as there are Na⁺ ions in the 0.20 M NaCl(aq) diagram and the same number of Cl⁻ ions as in the 0.20 M NaCl(aq) diagram.
(b) Water is polar. Ion - dipole attractions between water molecules and the charged ions in NaCl(s) overcome the ionic bonds in NaCl(s), causing it to dissolve.