How much heat is released if 2.00 moles
CF2Cl2 reacts with 70.0 g F2 with a 75.0
percent yield?
CF2Cl2 + F2 ! CF4 + Cl2
�H for this reaction is -401 kJ/mol rxn.
1. 553 kJ
2. 739 kJ
3. 985 kJ
4. 601 kJ
5. 1069 kJ
6. 802 kJ
Answer 1; 553 kJ
Well, it seems like you have a chemical equation there! But before we calculate the heat released, let's talk about the situation for a moment.
You mentioned a "75.0 percent yield." Now, I don't want to be a party-pooper, but yields can be a bit unpredictable, kind of like trying to catch popcorn with your mouth. So let's assume that 75% yield means that only 75% of the reactants actually go through the reaction and produce products.
Moving on to the calculation, we first need to find the limiting reactant (the reactant that is completely consumed). To do that, we need to convert grams of F2 to moles of F2.
Given that the molar mass of F2 is approximately 38 g/mol, we can calculate:
70.0 g F2 * (1 mol F2/38.0 g F2) = 1.842 moles F2
Since we know that 2.00 moles of CF2Cl2 are present, we compare the stoichiometric ratio of F2 to CF2Cl2 in the balanced equation (1:1) and find that CF2Cl2 is in excess.
Therefore, all 1.842 moles of F2 will react to produce products.
Now that we have the moles of F2, we can calculate the heat released:
Heat released = moles of F2 * �H
Heat released = 1.842 moles F2 * -401 kJ/mol
Heat released ≈ -738.542 kJ
So, rounding to three significant figures, the answer would be 2. 739 kJ.
That's a lot of heat! It's like holding a fire-breathing dragon in your hand. But remember, safety first! Don't try that at home, kids.
To calculate the amount of heat released in this reaction, you need to use the given information about the reaction stoichiometry and the percent yield.
First, determine the limiting reagent by calculating the moles of each reactant. The molar mass of CF2Cl2 is 121 g/mol (12.01 g/mol for C, 2 × 19.00 g/mol for F, and 35.45 g/mol for Cl), and the molar mass of F2 is 38.00 g/mol. So, for CF2Cl2, 2.00 moles × 121 g/mol = 242 g. Thus, CF2Cl2 is in excess.
For F2, the moles can be calculated using its molar mass: 70.0 g × (1 mol/38.00 g) = 1.842 moles.
The stoichiometric ratio between CF2Cl2 and F2 is 1:1, so the number of moles of Cl2 produced is also 1.842 moles.
Next, calculate the actual yield using the percent yield. The percent yield is given as 75.0%. To determine the actual yield, multiply the theoretical yield by the percent yield: 1.842 moles × (75.0% / 100) = 1.3815 moles.
Now, you can calculate the amount of heat released by multiplying the actual yield (in moles) by the enthalpy change per mole of reaction (-401 kJ/mol):
1.3815 moles × -401 kJ/mol rxn = -554.1 kJ
The negative sign indicates that heat is released in the reaction.
Therefore, the correct answer is option 1. 553 kJ.
First determine which is the limiting reagent. Use that to determine how much of the CF2Cl2 is used for 100% yield. Then 401 kJ/mol x mols CF2Cl2 use = kJ produced for 100% yield.
kJ produced x 0.75 = heat produced with 75% yield. This assumes that other reactions producing heat do not occur.