If you guys could let me know if I'm doing this right, and maybe continue to help me, I would greatly appreciate it. We had a sub, so I spent the whole class on the first question. It's been since Friday since I worked on it so my brain is a little... Fe2 O3 - y, if you know what I mean. Maybe help me with the steps so you don't feel like your doing my homework. Let me know if the pictures come out blurry.

Edited January 22, 201312 yr by NO+LiFe

Question 1:

(a), The ratio of NH4NO3:Na3PO4 is 3:1. 3 moles of NH4NO3 is approximately 240 grams while 1 mole of Na3PO4 is approximately 164 grams. 30 is 1/8 of 240. 1/8 of 164 is 20.5 grams. Clearly the limiting reagent is NH4NO3.
(b), As NH4NO3 is the limiting reagent, the maximum amount of moles of product is 1/8 of the amount of moles of each product in the equation. Thus, The maximum amount of (NH4)3PO4 formed is 1/8 moles and the maximum amount of NaNO3 formed is 3/8 moles. You can work out the rest from here.
©, This can be worked out using the information I gave you in (a).

Question 2:
(a), The ratio of CaCO3:FePO4 is 3:2. 3 moles of CaCO3 is 300 grams while 2 moles of FePO4 is 302 grams. 100 grams is 1/3 of 300. 1/3 of 302 is 100.6 grams. FePO4 is the limiting reagent.
(b) 45 grams of FePO4 is 14.9% of 302. Thus, 14.9% of 300 grams of CaCO3 reacts to form 14.9% of a mole of Ca3(PO4)2 and 14.9% of a mole of Fe2(CO3)3.
© This can also be worked out using the information I gave you in (a).

Question 3:

1 mole of Mg reacts to form 1 mole of H2. One mole of Mg is 24.3 grams. Thus, 40 grams is 1.65 moles of Mg. This can form 1.65 moles of H2.

Question 4:

This can be worked out by simply dividing the maximum amount of H2 that can form by the amount of hydrogen that actually formed, then using the resulting number to divide 100.

Edited January 22, 201312 yr by weiming1998

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Moderator Note

weiming,

 

Since this is the homework help section, it would be much appreciated if you could refrain from simply giving out the answers. In future, you should try asking simple questions that get students actively engaging in developing their own understanding thinking and lead them to the answer rather than simply giving it to them. In doing this, they will (hopefully) learn something from the experience and be able to apply themselves when it comes time to tackle other / harder problems.

 

It can also be pretty rewarding for you to be able to help someone in their understanding of a concept and have them actually get it.

Thank you guys! We had my teacher explain it to us the next day. I'm pretty sure I understand it now.