Chemical equations, please help test today.

[msdeannah]

Ok so what’s wrong with my logic. Here are some practice problems by teacher posted to help up study for the exam. Here are the word problems. My answer is in bold, the correct answer is not. What am I missing here? Oh and they are not balanced, I can do that once I write the equation right.

Aluminum oxide solid reacts with gaseous carbon monoxide to produce aluminum metal and carbon dioxide gas.

Al2O3(s) + CO(g) ® Al(s) + CO2(g)

AL2O3 +CO à AL3 + CO2

Ok here is my logic. Aluminim has a charge of +3 (I think)so why don’t I need a 3 subscript on Aluminum on the reactant side? (excuse me if my terminology is wrong)

Write and balance the equation showing the reaction between calcium metal and water to form aqueous calcium hydroxide and hydrogen gas.

Ca(s) +H2O(l)® Ca(OH)2(aq) +H2(g)

Ca 2 + H2O à Ca(OH)2 + H2

Samething here. Calcium is in column 2 which has a +2 charge, so why doesn’t it require a subscript of 2 on the product side?

This doesn’t happen often but, when it does (of course) everything else is messed up. Does anyone know what is wrong with my train of thought here?

Thanks for your help guys.

[Roberta88]

Okay, so say you had NaCl. Sodium is the cation since it is first and chlorine in the anion since it is second. When they are separate you do not write the charge. Na+1 just is Na, not Na1 (even if the charge is 2 or 3, you still do not write it). You only write it is linked to an anion. Na1Cl1, which since in this case both have subscripts of 1, you can just write NaCl.

Al2O3 + CO (pretend theres an arrow here) Al + CO2.

You do not write the charge of Al as a subscript because it is not linked to an anion on the right side. On the left side you do because it is linked to Oxygen and you put the charge of 3 from the Aluminum on the Oxygen. I hope this made sense...

[msdeannah]

Ohhhhhhhhhhhhhhhhhhhhhhhh!!!! That makes perfect sense. So when they are seperate, never write the charge? Could it really be that simple? Wow! Thanks :bowingpur

[NICUDreamer11]

Yeah, aubs is right, you only need the charge when an element is bonded with another. The charge of an element does not matter when it is alone - so the Al and Ca are written as is for that part. Hope you do good on your test!

[AtomicWoman]

Yeah, aubs is right, you only need the charge when an element is bonded with another. The charge of an element does not matter when it is alone - so the Al and Ca are written as is for that part. Hope you do good on your test!

Unless, of course, they are ions. In which case you do need the charge on the metal, even when it is by itself.

[msdeannah]

Thanks everybody. The teacher graded the test during lab.. I got a 96. The only question I got wrong was one I didn't even know about. It was on the back of the last page. i didn't even realize it was there.

Now we are starting on mole? I'm scared!! I have horror stories about this topic.

But for now celebration. Thanks.

[metalgirl70]

I didn't find mole factor conversions too bad, as long as you understand the factor label method.

[DesertRoseAZ]

Moles are not that bad. I remember learning it 2 weeks ago and being in tears. Luckily my husband is a chemist and got me to understand it. When you get to it, just remember to write out ALL units so you can cancel them correctly. As long as you do that you'll always get the right unit.

A cute saying my husband taught me with when I was stuck on what unit to go to next was....

Grams want to go to MoleTown. Moles love to get into ratios. Then it's time to go back to GramTown.

[NICUDreamer11]

Good job on your test msdeanah!

Oooh, moles...they are tough but luckily I learned them in my hs chem class so in college they weren't so hard. I don't really have any tips except learn them good now so you are not behind later! Conversions are probably the one of the most important things you will learn from chemistry for nursing. If you get it down now, you will have an easier time when they come up again!

Congrats again on your test!!!