Question

solarcaine aerosol spray is used for temporarily relieving pain as it works as a topical anesthetic numbing the skin. Solarcaine is in fact benzocaine, C9H11NO2 with molar mass 165.2g/mol. If a 100 ml spray contains 1.00g of benzocaine, calculate the pressure within the can and explain why it is likely to explode when heated in a fire where the tempreature maybe as high as 1300 degress celcuis.

Answer 1

Given volume of benzocaine , V = 100 mL = 0.1 L

         mass of benzocaine , m = 1.00 g

        molarmass of benzocaine , M = 165.2 g/mol

        number of moles of benzocaine , n = mass/molarmass

                                                              = 1.0 / 165.2 g/mol

                                                             = 6.05x10^-3 g/mol

       Temperature , T = 1300 ^oC = 1300 +273 K

                                 = 1573 K

We know that PV = nRT    R - gas constant = 0.0821 Latm/mol-K

So P = nRT / V

        = (6.05x10^-3 x 0.0821 x 1573 ) / 0.1

       = 7.81 atm

So the pressure within the can is 7.81 atm

At high temperature the vibrational energy of the molecules will be more thereby it cannot inbuilt in the can & the molecules came out resulting explosion.