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1) when a 3.25 g sample of solid sodium hydroxide wasdissolved in a calorimeter

ID: 687663 • Letter: 1

Question

1) when a 3.25 g sample of solid sodium hydroxide wasdissolved in a calorimeter in 100.0 g of water, the temperaturerose from 23.9 C to 32 C. calculate H ( in kj/mol NaOH) forthe solution process.                                  NaOH(s)-----Na +(aq) + OH(aq)    Assume it's a perfect calorimeter and thatthe specific heat of the solution is the same as that of purewater. 1) when a 3.25 g sample of solid sodium hydroxide wasdissolved in a calorimeter in 100.0 g of water, the temperaturerose from 23.9 C to 32 C. calculate H ( in kj/mol NaOH) forthe solution process.                                  NaOH(s)-----Na +(aq) + OH(aq)    Assume it's a perfect calorimeter and thatthe specific heat of the solution is the same as that of purewater.

Explanation / Answer


here heat gained/lost is = mc(T2-T1)
     where, m is the mass
           c is the specific heat capacity i.e 4.186 J/K-gm in case ofwater
           T2-T1 is the temperature change occuring
so heat gained = 100*4.186*(32-23.9) J                       = 3390.66 J                       = 3.390 KJ now molecular weight ofsodium hudroxide is = 23+ 16 + 1                                                                    = 40 gm so no of moles of itwhen 3.25 gm is taken = 3.25/40                                                                 = 0.08125 moles so now H (inKj/mol) = 3.390/0.0821                                    = 41.72 KJ/mol                       = 3390.66 J                       = 3.390 KJ now molecular weight ofsodium hudroxide is = 23+ 16 + 1                                                                    = 40 gm so no of moles of itwhen 3.25 gm is taken = 3.25/40                                                                 = 0.08125 moles so now H (inKj/mol) = 3.390/0.0821                                    = 41.72 KJ/mol