When 1.933 g of KNO3 is dissolved in 200 g of water initially at 23.57 ¢ªCelsius in a coffee-cup calorimeter, the final temperature is found to be 22.63 ¢ªCelsius. Calculate the heat released/absorbed per gram of KNO3 and per mol of KNO3 when KNO3 dissolves in water. NOTE: The heat capacity of calorimeter is 8.33 J ¢ªC-1. Assume the specific heat of the solution is the same as that of pure water
KNO3(s) + H2O ==> KNO3(aq)
The temperature DECREASED so the solution process is endothermic. Heat is absorbed.
q = mass H2O x specific heat H2O x (Tfinal-Tinitial) + Ccal*(Tfinal-Tinitial)
q = [200g H2O x 4.184 J/g*C x (22.63-23.57)] + [8.33(22.63-23.57)]
q = -?. That's for 1.933 g; therefore,
-?/1.933 is q/gram KNO3 which is part a.
For part b and q/mol take q/gram x molar mass KNO3.
To calculate the heat released/absorbed per gram of KNO3, we need to use the formula:
q = m * c * ΔT
Where:
q = heat released/absorbed
m = mass of KNO3
c = specific heat capacity of the solution (assumed to be the same as pure water)
ΔT = change in temperature
First, let's calculate the change in temperature (ΔT):
ΔT = final temperature - initial temperature
ΔT = 22.63 ¢ªC - 23.57 ¢ªC
ΔT = -0.94 ¢ªC
Now, let's find the heat released/absorbed per gram of KNO3 using the given data:
mass of KNO3 = 1.933 g
q = m * c * ΔT
q = 1.933 g * c * (-0.94 ¢ªC)
To find the specific heat capacity of the solution (c), we need to consider the heat capacity of the calorimeter (8.33 J ¢ªC^-1). The calorimeter absorbs some of the heat released/absorbed, so we need to take that into account.
The heat released/absorbed by KNO3 will be equal to the heat absorbed by the water and the calorimeter.
q = -q_calorimeter - q_water
q = - (8.33 J ¢ªC^-1 * ΔT) - (m_water * c_water * ΔT)
We need to consider the mass of water (200 g) and the specific heat capacity of water (4.18 J g^-1 ¢ªC^-1).
Now, let's substitute the values and calculate:
q = - (8.33 J ¢ªC^-1 * -0.94 ¢ªC) - (200 g * 4.18 J g^-1 ¢ªC^-1 * -0.94 ¢ªC)
Simplifying the equation:
q = 7.8162 J + 785.76 J
q = 793.5762 J
Now, let's find the heat released/absorbed per gram of KNO3:
Heat released/absorbed per gram of KNO3 = q / mass of KNO3
Heat released/absorbed per gram of KNO3 = 793.5762 J / 1.933 g
Finally, to calculate the heat released/absorbed per mol of KNO3, we need to consider the molar mass of KNO3, which is 101.1032 g/mol.
Heat released/absorbed per mol of KNO3 = (q / mass of KNO3) * molar mass of KNO3
Heat released/absorbed per mol of KNO3 = (793.5762 J / 1.933 g) * 101.1032 g/mol
By calculating the above equation, you will get the heat released/absorbed per gram and per mol of KNO3 when it dissolves in water.