When a 4.00g sample of KBr is dissolved in water in a calorimeter that has a total heat capacity of 2.908 kJ x K^-1, the temperature decreases by .230 K. Calculate the molar heat of KBR
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To calculate the molar heat of KBr, we need to use the formula:
q = mCΔT
Where:
- q is the heat transferred (in joules),
- m is the mass of the substance (in grams),
- C is the heat capacity of the calorimeter (in J/K),
- ΔT is the change in temperature (in Kelvin).
First, we need to convert the mass of KBr to moles. We can do this by dividing the mass by the molar mass of KBr. The molar mass of KBr can be calculated by adding the atomic masses of potassium (K) and bromine (Br) from the periodic table.
The atomic mass of K is 39.10 g/mol, and the atomic mass of Br is 79.90 g/mol. So, the molar mass of KBr is:
Molar mass of KBr = 39.10 g/mol + 79.90 g/mol = 119.00 g/mol
Now we can calculate the number of moles of KBr in the 4.00g sample:
Number of moles of KBr = mass of KBr / molar mass of KBr
Number of moles of KBr = 4.00g / 119.00 g/mol = 0.0336 mol
Next, we need to calculate the heat transferred (q) using the formula mentioned earlier. Rearranging the formula, we have:
q = mCΔT
Given that the heat capacity of the calorimeter (C) is 2.908 kJ/K, we need to convert it to joules:
Heat capacity of calorimeter (C) = 2.908 kJ x 1000 J/1 kJ = 2908 J/K
Now we can substitute the given values into the formula:
q = (0.0336 mol) * (2908 J/K) * (0.230 K)
q = 0.543 J
The heat transferred (q) is 0.543 Joules. This represents the amount of heat released by the dissolution of the KBr sample.
Finally, we can calculate the molar heat of KBr by dividing the heat transferred (q) by the number of moles of KBr:
Molar heat of KBr = q / number of moles of KBr
Molar heat of KBr = 0.543 J / 0.0336 mol
Therefore, the molar heat of KBr is approximately 16.16 J/mol.
moles KBr = 4.00/molar mass = ??
2.908 kJ/K x 0.230 K = ?kJ.
Then molar heat of KBr = ?kJ/?mole.