<p>So on the test today we got an impossible chem problem. It was so.... hard.
We had like at least 30 minutes for this one problem and nobody I talked to could do it.</p>
<p>It was something like this</p>
<p>A mixture of CH4 and C2H6 are burned with oxygen to make a mixture of Water and Carbon Dioxide.
The original weight of the mixture is like 10.0g (near that) and the weight of all end products are 60.0g. Find the percent mass of methane in the original mixture.</p>
<p>Mm…Stoich. Ugh…we did an example problem like this 2 days ago and I have no clue what happened. And yet I have a quiz on it in 2 days D:</p>
<p>If I remember correctly how to do something like this…</p>
<p>So what you need to do is to create a system of equations to solve for 2 unknowns, x and y. In this case, you have x CH4 and y C2H6, as you do not know how many parts of each were used. The mass equals 10.0g, so the first equation would be xCH4 + yC2H6 = 10.0g. I don’t quite know what the second equation would be, as I am a bit tired atm. Anyways, the second equation is to contain the percent composition of either the hydrogen or oxygen or whatever, and these percentages would translate to your second equation (like 0.3608x + 0.5112y = 50.0g). You solve for 1 variable, plug that into the first equation, and solve for y. And then you do it for x. Eventually you’ll see how many parts were CH4, and how many were C2H6, and you just do simple percent composition calculations to reach a final percentage.</p>
<p>Brutal, it’s absolutely brutal. I feel you. This stuff is pretty insane…</p>
<p>Ugh, the problem is that the C, H and O on each side split into 2 parts or combine into one. And they conveniently combine/split into the mixtures, so you don’t know how much of each is in one. Equations don’t seem to work because you don’t know how much of each is in the mixture, and setting variables is odd because on the other side of the equation the variables are not the same because they are split up.</p>
<p>I finihsed AP Chem last year (took pre-ap chem 1 soph year) and made all 99+'s and don’t have a clue what that problem is asking! There is a reason no one in my school has ever passed the AP Chemistry Exam.</p>
<p>Reading this problem makes a small part of me miss chemistry. I liked the feeling of figuring out complex problems. But then I remember how much I hated the notes, and the labs, and the homework, and pretty much everything else to do with chem.</p>
<p>^Same. I just pulled out my old AP chem bible and started looking for a periodic table to start figuring this out. It brought back memories, man.</p>