A 2.461-g sample of glutamic acid, C5H9NO4 (147.13 g/mol) was burned in a bomb calorimeter with
excess oxygen. The temperature of the calorimeter and the water before combustion was 23.76 °C; after
combustion the calorimeter and the water had a temperature of 29.46 °C. The calorimeter had a heat capacity of
660 J/K, and contained 1.405 kg of water. Use these data to calculate the molar heat of combustion (in kJ) of
glutamic acid
I got 2003 kj/mol (think its right)
Metallic Cd reacts with hydrochloric acid according to the following equation:
Cd (s) + 2 HCl (aq) → CdCl2 (aq) + H2 (g)
The enthalpy change associated with this reaction can be determined with an ice calorimeter. If 10.88 g of ice
are melted when 5.778 g of Cd reacts with excess hydrochloric acid, what is ∆H (in kJ/mol Cd) for the reaction
written above? The heat of fusion of ice is 333 J/g.
I got 70.5 Kj/mol (not sure about this one)
Alos my sig figs matter!
Thanks so much
To calculate the molar heat of combustion of glutamic acid, you can use the equation:
q = mcΔT
where:
q = heat absorbed or released
m = mass of water
c = specific heat capacity of water (4.184 J/g·°C)
ΔT = change in temperature (final temperature - initial temperature)
First, calculate the heat absorbed or released in the calorimeter using the formula:
q_calorimeter = m_calorimeter · c_calorimeter · ΔT_calorimeter
where:
m_calorimeter = mass of water in the calorimeter (in kg)
c_calorimeter = specific heat capacity of the calorimeter (660 J/K)
ΔT_calorimeter = change in temperature of the calorimeter (final temperature - initial temperature)
Next, calculate the heat absorbed or released by water using the formula:
q_water = m_water · c_water · ΔT_water
where:
m_water = mass of water (in kg)
c_water = specific heat capacity of water (4.184 J/g·°C)
ΔT_water = change in temperature of the water (final temperature - initial temperature)
Now, calculate the total heat absorbed or released in the system (q_system) by subtracting the heat absorbed or released by the calorimeter (q_calorimeter) from the heat absorbed or released by the water (q_water):
q_system = q_water - q_calorimeter
Next, calculate the moles of glutamic acid burned by dividing the mass of glutamic acid by its molar mass:
moles of glutamic acid = mass of glutamic acid / molar mass of glutamic acid
Finally, calculate the molar heat of combustion by dividing the total heat absorbed or released in the system (q_system) by the moles of glutamic acid burned:
molar heat of combustion = q_system / moles of glutamic acid
Substituting the given data into the equations, you can now calculate the molar heat of combustion of glutamic acid.
Regarding the enthalpy change (∆H) for the reaction of metallic Cd with hydrochloric acid, you need to use the equation:
∆H = -q / moles of Cd
First, determine the heat absorbed or released by the system (q) using the equation:
q = mass of water melted · heat of fusion of ice
Then, calculate the moles of Cd used in the reaction by dividing the mass of Cd by its molar mass:
moles of Cd = mass of Cd / molar mass of Cd
Finally, substitute the values into the equation ∆H = -q / moles of Cd to determine the enthalpy change (∆H) for the reaction. Don't forget to convert the units to kJ/mol.
Note: Regarding significant figures, make sure to use the appropriate number of significant figures in your calculations and round the final answer to the correct number of significant figures based on the given data.