[Fish200398]

5.5 g KOH dissolve in 100 mL water at 19.5 C (in calorimetry jar). after that the temperature increase into 30.5 C. what heat dissolving of KOH in J/g
(C water = 4,18 kJ/mol)
(water density = 1g/ml)
Options : 4,850.9
4,598
2,299.0
882.0
836.0
is this question has error, that is
C water supposed to be = 4,18 kJ/(g C)
and the answer supposed to be in kJ?
and when we calculate Q = mc delta T = 105.5 g . 4,18Kj/(g C) . 11 C = 4,850.9 kJ not J/g

[AWK]

Why 105.5

[Borek]

C water = 4,18 kJ/mol

Something wrong here, should be 4.18 J/(g*deg), not per mole.

C water supposed to be = 4,18 kJ/(g C)

A bit better, but still wrong, not kJ but just J.

Why 105.5

Total mass of the final solution, common approximation/approach in a HS level problems.

[Fish200398]

btw, 4,850.9 J divided by 105.5 g = 45.980 J/g....

[AWK]

You should calculate

heat dissolving of KOH in J/g

- gram of KOH, not gram of KOH solution.

[Fish200398]

ok. btw is it really 4,180 J/(g C) not 4,180 J/mole in the calculation,

[MNIO]

first of all, some assumptions
  (1) the resulting solution has mass = 105.5g.  100mL = 100g H2O + 5.5g KOH
  (2) the resulting solution has the same Cp as H2O = 4.184 J/g°C      J not kJ
  (3) all heat produced raised the temp of the liquid solution.

then
  Q = m*Cp*dT
     = 105.5g * 4.184 J/g°C * (30.5°C - 19.5°C)
     = 4855 J

that is based on 5.5g of KOH so heat of dissolution per gram is
   ΔHsolution = 4855 J / 5.5g = 882 J/g

and if you want kJ / mole of KOH then we can easily convert
        4855J       56.11g KOH      1 kJ
   ------------- x --------------- x ------- = 49.5 kJ/mol
     5.5g KOH      1 mol KOH      1000J

(the literature value for the dissolution of KOH in H2O @ 25°C = 57.6 kJ/mol so this result is off by 14%)

**********
now let's look at your possible choices
   4,850.9
   4,598
   2,299.0
   882.0
   836.0
with NO units shown

since the problem states "what heat dissolving of KOH in J/g" let's assume those units are J/g in which case 882.0 is the correct choice.

**********
units are IMPORTANT !!!  please include them on all future questions.
so are sig figs.  100.0mL vs 100 mL are the difference between 882 J/g and 800 J/g in your result

[Fish200398]

so, the 4,180 J/mole there is no such as that and maybe error printing? instead 4,180 J/gC?

[Borek]

so, the 4,180 J/mole there is no such as that and maybe error printing? instead 4,180 J/gC?

An obvious error, mole used instead of g.