When a 6.50-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 21.6 degrees C to 37.8 degrees C. Calculate delta H (in kJ/mol NaOH) for the solution process. Assume that the specific heat of the solution is the same as that of pure water.

Respuesta :

Total mass = 100 + 6.5 = 106.5 g
Specific heat of water = 4.18 Joules/gram °C

Q = mCpΔT
Q = 106.5 x 4.18 x (37.8 - 21.6)
Q = 7177 Joules
Moles of NaOH:
6.5 / (23 + 16 + 1)
= 0.1625

Enthalpy of reaction: 7177/0.1625
= 441.7 kJ/mol NaOH

441.7 kJ/mol is the delta H (in kJ/mol NaOH) for the solution process. When a 6.50-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 21.6 °C to 37.8 °C.

What is specific heat capacity?

The specific heat capacity is defined as the quantity of heat (J) absorbed per unit mass (kg) of the material when its temperature increases 1 K (or 1 °C), and its units are J/(kg K) or J/(kg °C).

Specific heat of water = 4.18 J/g °C

Total mass = 100 + 6.5 = 106.5 g

Q = mCpΔT

Q = 106.5 x 4.18 x (37.8 - 21.6)

Q = 7177 Joules

Moles of NaOH:

Moles = [tex]\frac{mass}{molar \;mass}[/tex]

Moles = [tex]\frac{6.5}{23 + 16 + 1}[/tex]

= 0.1625

Enthalpy of reaction: [tex]\frac{7177}{0.1625}[/tex]

= 441.7 kJ/mol NaOH

Hence, 441.7 kJ/mol is the delta H (in kJ/mol NaOH) for the solution process. When a 6.50-g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 21.6 °C to 37.8 °C.

Learn more about specific heat capacity here:

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