question_answer

  Benzoic acid is used as a food preservative. The graph below shows the heating curve for benzoic acid. Study the graph and answer the following questions (i) At what time does benzoic acid begin to (a) melt?                              (b) boil? (ii) What is the melting point of benzoic acid? (iii) What happens to -the temperature while benzoic acid melts? (iv) What is the physical state of benzoic acid during the time interval of 35-45 min?

Answer:

                  (i) (a) Benzoic acid begin to melt at 20 min. (1) (b) Benzoic acid begin to boil at 52 min. (1) (ii) The melting point of benzoic acid is 120° C. (1) (iii) The temperature remains constant at 120  ° C untill all the benzoic acid has melted.      (1) (iv) The physical state of benzoic acid is liquid during the time interval of 35-45 min.         (1)