bloody need help ,urgent (1 Viewer)

[Dr.Dan]

anyone who has conquering chem-prelim please help me with questions 34 all. on page 226

otherwise these are questions for general public


34.calculate molar heat for the ionic substance involved in each of the following carried out in insulated plastics using a thermometer which read at 0.1C.Take specific heat capacity of final solutions as 4.2J K-1 g-1.

a) 5.3g calcium chloride was dissolved in 250ml (=250g) water at 18.6C . the temperature rose to 22C.



Just need help with that 1 please.............

 

[brenton1987]

Lets see if I remember how to do these properly.

ΔH = - m C ΔT

= - 250 (g) * 4.2 (J/K/g) * 3.4 (K)
= -3.57 * 10³ J
= -3.57 kJ


Moles of CaCl₂ = 5.3 / 110.986
= 4.77537... * 10^-2

= -3.57 / 4.77537... * 10^-2
= -7.4758... * 10¹
= -7.5 * 10¹ kJ/mol



What does the book say?

 

[independantz]

Yeah the method is correct.

 

[Dr.Dan]

thx guys... life saver