Question

Determine how much heat is needed to warm up 10.0 g of ammonia, NH3, from -50.0°C to 0.00°C. The table below lists information about ammonia that will help you solve the problem. Show all your work. Melting point = -77.73°C Boiling point = -33.4°C AHfus = 5.653 kJ/mol AHvaa = 23.35 kJ/mol Cn(liquid ) = 37.0 J/mol.K Cn(gas) = 80.8 J/mol-K

Answer 1

Given: 10.og melting Now, it boiling point. mass of ammonia, NH3, ma Initial temperature, T = -50% final temperature, If = 0.00°c Solution: since, melting point = -77.73°C f boiling point= - 33.46 which indicates that initially ammonia is in biquid state, because initial temperature is in betwen point and we start heating liquid ammonia, it will start boeling at 33.4°C Therefore, ammonia will be inliquid state from Ty = -50c to To = - 33.4°c (boiling point) and after To = -33.4¢ to = 0.00°c ammoria will be in gaseous state. calculation, Heat required from Ti = -50C to To = -33.4°C, mcnAT n= number mal of Niz Id NH Squad NH” 0.59 modx 37.05/. *(To-Ts) Cliq. NH2) = 91.76 * (-33.4c-(-50€) - 91.76 x 16.6 361.3 J = n.ohrab boiling, Quak = 0.59 mal X 33.3567/mes Tf mass mol. of Niya molar mass n= 10g 17 g/mol 0.59 mal NH₂ n Quig N3 = Heat required during Qvap = 13.7765 kJ Qvab = 13776.55

Heat require to raise the temperature from To= - 33.4 & to T=0.00€ Q Qgas AT = 0.59 med x 80.85/m.** (0,00€ – (-33.4C)) n Cn (gas) = 0.59 x 80.8 x 33.4 J 11 1592.95 J Qgas Over all heat required to warm up log NH3 from T; = -50% to To= 0.0°C is Ptotal = Qlig (WH) + Prap + Q 'gas Ptotal - 361.33 + 1377653 + 159 2.255 Gtotal = 15730.055

Since the initial temperature lies between the melting point and the boiling point of the ammonia. That means the ammonia is in the liquid state. The final temperature is higher than the boiling point, that is the final state of the ammonia is the gaseous state.

Now, we have to heat the liquid ammonia at the temperature -50.0 degree centigrade to the gaseous ammonia at the temperature 0.00degree centigrade.

This will occur in three steps,

Step 1, Heating liquid ammonia up to the boiling point

Step 2, Heating during vaporisation of ammonia at the boiling point,

Step 3, Heating gaseous ammonia after the vaporization of the ammonia.

Finally, add all the heat supplied during these three steps that will be the answer.