Question

Which member of each pairs is more soluble in water?

a)MgBr2(s) or CH3CH2MgBr(s)

b)MgO(s) or SiO2

c)CH2C!(!) or CC!4(!)

d)CH3CH2OCH2CH3 or CH3CH2OH

Answer 1

Answer 2

 Calculation/Explanation:

a) MgBr₂(s) or CH₃CH₂MgBr(s)

• MgBr₂: Ionic compound → dissociates into Mg²⁺ and Br⁻ ions in water → highly soluble.

• CH₃CH₂MgBr: Polar but has a large organic (hydrocarbon) part → less soluble than ionic MgBr₂.
  Winner: MgBr₂ (ions > polar organics).

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b) MgO(s) or SiO₂(s)

• MgO: Ionic (Mg²⁺ and O²⁻) → dissolves well in water.

• SiO₂: Network covalent (giant sand-like structure) → doesn’t dissolve.
  Winner: MgO (ionic beats covalent networks).

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c) CH₂Cl₂(l) or CCl₄(l)

• CH₂Cl₂: Polar (δ⁺ on H, δ⁻ on Cl) → mixes with polar water.

• CCl₄: Symmetrical/nonpolar → "oil-like," repels water.
  Winner: CH₂Cl₂ (polarity wins).

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d) CH₃CH₂OCH₂CH₃ or CH₃CH₂OH

• CH₃CH₂OCH₂CH₃ (ether): Mildly polar but no H-bonding.

• CH₃CH₂OH (alcohol): Forms H-bonds with water → much more soluble.
  Winner: CH₃CH₂OH (H-bonding rules).

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Short Answer:
a) MgBr₂
b) MgO
c) CH₂Cl₂
d) CH₃CH₂OH