This problem is very easy to answer. You simply have to look at the subscripts of each element of the compound.
1. For caffeine, which has a molecular formula of C₈H₁₀N₄O₂, it contains 8 atoms of Carbon, 10 atoms of Hydrogen, 4 atoms of Nitrogen and 2 atoms of Oxygen.
2. For Iron(III) Sulfate, which has a molecular formula of Fe₂(SO₄)₃, it contains 2 atoms of Iron, 3 atoms of Sulfur, and 12 atoms of Oxygen.
Answer:
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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!
Your body uses it to build and repair tissue. You need it to make enzymes, hormones, and other body chemicals. It is an important building block of bones, muscles, cartilage, skin, and blood. Along with fat and carbohydrates.
