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AAMC Practice Test FLE 1
Keira_6444
#1 Posted : Wednesday, July 14, 2021 1:31:03 AM
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Passage 10 #54: Are you able to explain why C is the answer? The explanation only says its right because it is balanced but to me, they all look balanced. Also, how are we supposed to determine whether the Al (s) or the Cu (s) is on the reactant side vs the product side of the equation?

Thanks!
INSTR_Katrina_128
#2 Posted : Friday, July 16, 2021 9:58:14 PM
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Hi Keira!

Great question. The explanation doesn't provide very much detail, unfortunately. 😥

Take a look at B and D, first. Focus on the charges. In B, there are 3(3+) on left and 2(2+) on the right. The charges aren't balanced! Similarly, for D, there are 2(2+) on the left and 3(3+) on the right. The charges also aren't balanced! So, B and D cannot be correct!

For A and C, both have 2(3+) or 3(2+) on the left and right, indicating a balnace of charges. So which one is correct?

Take a look at the table. In the first row and second column, the table tells us that a mixture of Al3+(aq) and Cu(s) gives NO CHANGE. This means that Al3+(aq) DON'T REACT. Took a look at reaction A. If Al3+(aq) and Cu(s) don't react, then how can reaction A proceed? 😮

By process of elimination, only C remains. Click and you're done!

You can confirm that it must be true (if you really want to), by seeing that Cu2+(aq) and Al(s) produces a new solid (second row, first column of the table).

Let me know if that helps. 😀
Keira_6444
#3 Posted : Saturday, July 17, 2021 8:25:44 PM
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yes that is very helpful thank you!
INSTR_Calla_139
#4 Posted : Thursday, July 29, 2021 9:18:10 PM
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Good Luck with everything:)
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