Question

Chromium (Cr) can combine with chlorine (Cl2) to form chromium chloride (CrCl3). Which equation is a correct representation of this reaction?









A.

Cr + Cl2→ CrCl3








B.

2Cr + Cl2→CrCl3








C.

2Cr + 3Cl2→CrCl3








D.

2Cr + 3Cl2→ 2CrCl3

Answer 1

D. notice how on each side of the equation everything is the same. (3Cl2 means 3 Cl2 atoms, 3x2=6. and 2CrCl3 means 2 Cr atoms, already the same on the left, and 2 Cl3 atoms, 2x3=6)
a correct representation means the equation has to be balanced.
\[Cr+Cl _{2} \rightarrow CrCl _{3}\]
Cr on both sides are the same. so they're cool. but Cl on both sides are not the same, therefore it's unbalanced. so to balance it out, first we need to add a coefficient. in this case that would be 2 to Cr on both sides. but why, I thought Cr was cool right? well, the coefficient isn't just for the Cr, it's also for Cl, which is what we need to change, so Cr is changing in the process too.
Ok, so now you should have \[2Cr+Cl _{2} \rightarrow 2CrCl _{3}\]
to match the left Cl with the right Cl we have to make 6 Cl atoms. we only have 2 right now on the left. so we put a coefficient of 3 in front of that sucker and BAM! we've got 6 Cl atoms, just what we needed.
so now we've got \[2Cr+3Cl _{2} \rightarrow 2CrCl _{3}\] AKA a balanced chemical equation.

I hope I explained it ok if not we can call in an expert
I literally just learned how to do this like an hour ago so I'm very pleased with myself that I actually know how to do it omg