Below are data from a calorimetric determination of Delta H_sol for an unknown s

Question

Below are data from a calorimetric determination of Delta H_sol for an unknown salt. (Refer to part C of the procedure). Calculate the enthalpy of solution per gram of salt, assuming that C_p.cal is entirely attributable to the water (as in question 2). Identify the salt from the list in the above table. Why is T_f obtained by extrapolating temperature to time t = 0 s? mass of calorimeter: 9.42 g mass of calorimeter + water: 107.76 g mass of calorimeter + water + salt: 109.67 g initial calorimeter temperature: 22.98 plusminus 0.05 degree C (See Figure 2.) final calorimeter temperature: 21.89 plusminus 0.05 degree C

Explanation / Answer

mass of water = 107.76-9.42 = 96.34 gm

mass of salt = 109.67-107.76=1.91 gm

enthalpy change = mass of waterr* specific heat of water* temperature difference

= 96.34*4.184*{-(22.98+-0.05)+ (21.89+-0.05} = -439.4 Jojules

enthalpy change per mass of water = -439.4/1.91 =230.034 Joules/gm.

The dissolution is endothermic as indicated by drop in temperature.

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