Question

Briefly explain the reasoning for the following:

1. CH4 has a lower melting point than C4H10

2. Dimethyl ether (CH3OCH3) has a lower vapor pressure than propane (CH3CH2CH3) at the same temperature.

3. NaCl has a higher melting point than NaBr.

4. Copper conducts electricity but copper II sulfate (CuSO4) doesn't.

Answer 1

1) CH4 molar mass is lower than C4H10 . if molar mass increases intermolecular forces increases and melting point also increases. so C4H10 has greater melting point

2) CH3OCH3 molar mass is higher than CH3CH2CH3 so is has greater boiling point than CH3CH2CH3 . if boiling point is more means vapoure pressure is less.

3) NaCl has higher melting point than NaBr . it is due to NaCl lattice enrgy is more compared to NaBr. if lattice energy increases we need to give more temperature to melt that crystal

4) in copper metal there will be mobile electrons are present . these are circulated throught out the copper metal so it conduct electricity . but CuSO4 even though unpaied electron it is bad conductor in solid state .