- #1

MacLaddy

Gold Member

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## Homework Statement

Nitric Acid is produced via the following equation:

[itex]3NO_2 + H_2O \rightarrow 2HNO_3 + NO[/itex]

How many grams of [itex]NO_2[/itex] are required to produce 7.50 grams of [itex]HNO_3[/itex]?

## Homework Equations

[itex]HNO_3 = 138 amu[/itex]

[itex]NO_2 = 126 amu[/itex]

## The Attempt at a Solution

I think I have a solution to this, but formulating these equations does not click in my head properly. I see other people do it over and over, but it hasn't clicked yet.

[itex]7.50g HNO_3 * \frac{138g NO_3}{126g HNO_3}=8.21g NO_2[/itex]

I'm getting mixed up by thinking that this may be a shortcut. Well actually, I'm mixed up on a lot of it, like why can you just divide [itex]\frac{138g NO_3}{126g HNO_3}[/itex]? I can see how it works nicely and how handy it is, but it's not intuitive to me yet so I'm having a hard time processing it.

Also, should I be adding Moles to the equation above, like this

[itex]7.50g HNO_3 * \frac{138g NO_3}{1 Mol NO_3}*\frac{1 Mol HNO_3}{126g HNO_3} =8.21g NO_2[/itex]

and then perform the arithmetic? However, if I do it that way I cannot cross out some of the components properly.

Any advice would be appreciated. I don't know why but Chemistry isn't clicking the way I was hoping it would. I'm not having nearly this much trouble in my calc class.