Question

Which of the following is not true? a. The freezing point of sea water is lower than the freezing point of pure water. b. The boiling point of a water sample from the Salt Lake is lower than the boiling point of pure water. c. The freezing point of 0.1 M NaCl is lower than the freezing point of 0.05 M NaCl.

Answer 1

b. The boiling point of a water sample from the Salt Lake is lower than the boiling point of pure water: FALSE

Salt lake contain NaCl as impurities. when salt (NaCl) is added in pure water then its boiling point get increases because attraction increases between ions present in water so more energy is require to break the force between ions so boiling point of salt lake will bre higher than pure water. So boiling point of salt lake will not get lower.

a. The freezing point of sea water is lower than the freezing point of pure water: TRUE

Freezing point of sea water is lower than pure water because in salt water NaCl is present which prevent the water molecule to transform from liquid phase to solid phase.

c. The freezing point of 0.1 M NaCl is lower than the freezing point of 0.05 M NaCl: TRUE

freezing point depend upon number of molecules are dissociated in solution more the number of molecules will be in solution , lower will be freezing point. 0.1 M (high concentration ) NaCl contain greater number of molecules of NaCl compare to 0.05 M(lower concentration)  NaCl. So freezing point of 0.1M NaCl will be lower than 0.05M NaCl.