Answer:
Mole fraction of C₄H₄S = 0.55
Explanation:
Mole fraction is moles of solute / Total moles
Total moles are the sum of moles of solute + moles of solvent.
Let's find out the moles of our solute and our solvent.
Mass of solute: 55g
Mass of solvent: 65g
Mol = Mass / molar mass
55 g / 84.06 g/mol = 0.654 moles of C₄H₄S
65 g /123 g/mol = 0.529 moles of C₂H₃BrO
Total moles = 0.654 + 0.529 = 1.183 moles
Mole fraction of thiophene = Moles of tiophene / Total moles
0.654 / 1.183 = 0.55
Answer: The correct answer is -297 kJ.
Explanation:
To solve this problem, we want to modify each of the equations given to get the equation at the bottom of the photo. To do this, we realize that we need SO2 on the right side of the equation (as a product). This lets us know that we must reverse the first equation. This gives us:
2SO3 —> O2 + 2SO2 (196 kJ)
Remember that we take the opposite of the enthalpy change (reverse the sign) when we reverse the equation.
Now, both equations have double the coefficients that we would like (for example, there is 2S in the second equation when we need only S). This means we should multiply each equation (and their enthalpy changes) by 1/2. This gives us:
SO3 —>1/2O2 + SO2 (98 kJ)
S + 3/2O2 —> SO3 (-395 kJ)
Now, we add the two equations together. Notice that the SO3 in the reactants in the first equation and the SO3 in the products of the second equation cancel. Also note that O2 is present on both sides of the equation, so we must subtract 3/2 - 1/2, giving us a net 1O2 on the left side of the equation.
S + O2 —> SO2
Now, we must add the enthalpies together to get our final answer.
-395 kJ + 98 kJ = -297 kJ
Hope this helps!
Percent error is the difference between the measured and known value, divided by the known value, multiplied by 100%.
So first, we take our measured value, .299 cm, minus our known value, .225 cm.
.299 cm - .225 cm=.004 cm
Next, we divide that by our known value
Finally, multiply your answer by 100
.0177777778 x 100= 1.77777778 %
Round to three significant figures, and you're done.
=1.78 % error
Im just guessing, so i think is A
