How many kilojoules are absorbed when 266 g of PCl5 reacts?
PCl5(g)→PCl3(g)+Cl2(g)ΔH=+67kJ
To calculate the amount of energy (in kilojoules) absorbed when 266 g of PCl5 reacts, we need to use the molar mass of PCl5 and the molar ratio between PCl5 and the absorbed energy.
1. First, calculate the number of moles of PCl5:
Number of moles = mass / molar mass
Number of moles = 266 g / (30.97 g/mol + 5 * 35.45 g/mol) (use the atomic masses of P and Cl from the periodic table)
Number of moles = 266 g / 208.45 g/mol
Number of moles = 1.276 mol (rounded to three decimal places)
2. Now, we need to use the balanced chemical equation to determine the molar ratio between PCl5 and the absorbed energy. From the equation:
PCl5(g) → PCl3(g) + Cl2(g) (ΔH = +67 kJ)
The coefficient of PCl5 is 1, which represents 1 mole.
The ΔH value of +67 kJ corresponds to the reaction of 1 mole of PCl5.
3. Finally, calculate the energy absorbed when 1.276 moles of PCl5 reacts:
Energy absorbed = (Energy change per mole) x (Number of moles of PCl5)
Energy absorbed = +67 kJ/mol x 1.276 mol
Energy absorbed ≈ +85.41 kJ
Therefore, approximately 85.41 kilojoules are absorbed when 266 g of PCl5 reacts.
To determine the amount of energy absorbed when 266 grams of PCl5 reacts, we can use the concept of molar mass and stoichiometry.
First, we need to calculate the number of moles of PCl5. To do this, we divide the given mass by the molar mass of PCl5. The molar mass of PCl5 can be calculated by summing the atomic masses of each element in the compound:
Molar mass of PCl5 = (1 mol of P) + (5 mol of Cl)
= (1 * atomic mass of P) + (5 * atomic mass of Cl)
= (1 * 30.97 g/mol) + (5 * 35.45 g/mol) (using periodic table values)
= 30.97 g/mol + 177.25 g/mol
= 208.22 g/mol
Next, we calculate the number of moles of PCl5:
Number of moles of PCl5 = Mass of PCl5 / Molar mass of PCl5
Number of moles of PCl5 = 266 g / 208.22 g/mol
Now, we can use the stoichiometry of the balanced equation to determine the energy absorbed. From the balanced equation, we can see that 1 mole of PCl5 produces 67 kJ of energy. Therefore, we can set up the following proportion:
67 kJ / 1 mole = x kJ / (moles of PCl5)
To find the value of "x," we multiply the moles of PCl5 by the ratio obtained from the proportion. Thus, the energy absorbed when 266 g of PCl5 reacts can be calculated as follows:
Energy absorbed = (Number of moles of PCl5) * (67 kJ / 1 mole)
By plugging in the calculated value for the number of moles of PCl5, we can find the amount of energy absorbed.