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Chemistry/ Dr.Bob222

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DrBob222 I am beginning to understand about balancing equations well, thanks to your help, but there are still some other things, which I am having a hard time figuring out.

Complete and balance the following chemical reactions between an acid and a metal.

A) HBR + Mg ->

This is confusing for me, how do I balance this out?

There was a similar example like this in the book and it was ....

HBr + Al =

6HBr + 2Al -> 2AlBr3 + 3H2.

My questions are that how did they get "6" Hbr? Also where did the 2Al come from, For the product part, I know that the three comes from Aluminum, but why do they not add it in the first part. This is really confusing me now, I think I'm forgetting this whole balancing stuff. DrBob222 please bring me back on track.

  • Chemistry/ Dr.Bob222 - ,

    A) HBR + Mg ->

    This is confusing for me, how do I balance this out?
    First, write the products.
    HBr + Mg ==> MgBr2 + H2
    Next, balance with coefficients.
    2HBr + Mg ==> MgBr2 + H2
    Finally, check it.
    I see 2 H on both sides.
    I see 2 Br on both sides.
    I see 1 Mg on both sides.
    Good. Balanced.


    There was a similar example like this in the book and it was ....

    HBr + Al =
    Write the produces.
    HBr + Al ==> AlBr3 + H2
    Balance with coefficients.
    I note quickly that I need a 2HBr to balance H on the right but a 3HBr to balance Br on the right. When that happens, we know neither 3 nor 2 will work so we go with 6.
    6HBr + 2Al ==> 2AlBr3 + 3H2.
    Finally, check it.
    I see 6 H on left and right.
    I see 6 Br on left and right.
    I see 2 Al on left and right.
    Good. Balanced.


    6HBr + 2Al -> 2AlBr3 + 3H2.

    My questions are that how did they get "6" Hbr? Also where did the 2Al come from, For the product part, I know that the three comes from Aluminum, but why do they not add it in the first part. This is really confusing me now, I think I'm forgetting this whole balancing stuff. DrBob222 please bring me back on track.
    The 2 for 2AlBr3 is used because that's the only way to get 6 Br atoms and that forces us to place a 2 for Al on the left.

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