Reaction between Tin and Nitric Acid lab discussion Help

[kratious]

Hello! We took Tin granules measured them in a crucible, with a petri dish to get the weight. We then added about 100 drops of 10M HNO3 and let that sit for 10 mins and heated it, cooled, weighed it, then repeated the heat, cool and weight again.

Here's my data:

     Mass of petri dish, crucible, and cover: 58.771g

     Mass of petri dish, crucible, cover, and tin granules: 59.761g

     Mass of reaction after first heating: 60.024g

     Mass of reaction after second heating: 60.020g

Here is the report question:

  1.)  From the mass of tin and the mass of tin oxide, calculate the mass of oxygen that combined with tin. From the masses of the tin and oxygen, calculate the number of moles of each. Express the compounds's empirical formula as Sn1Ox, where x is expressed to 3 significant figures, e.g., SnO2.34. Round x to the nearest integer. Calculate the percent error of x from the integer. 

 

    I emailed the professor no response yet so I'm just searching where ever. I understand the concept of g to moles and moles to g and how to get from % to empirical formula. I just don't understand where to start from here. Does it want my mass of 60.020g - 58.771g ? Is that the mass of the tin oxide I had? 

[hypervalent_iodine]

You need both the mass of tin you started with, and the mass of your product. 

2 hours ago, kratious said:

Does it want my mass of 60.020g - 58.771g ? Is that the mass of the tin oxide I had? 

What do you think? If you assume your reaction went to completion (ie. all the tin reacted to make tin oxide), what does the 60.020 g represent (what is in it)?

[Country Boy]

Didn't your teacher, or text book, explain what a "mole" is?  One mole of any substance contains "Avogadro's number" of molecules of that substance and that number is chosen so that the mass of one mole of a substance, in grams, is equal to that substance's molecular weight.  For example, carbon-12 has a molecular weight of 12 atomic units (au) (Any form of carbon has 6 protons.  The isotope, carbon 12, also has 6 neutrons which have the same weight as the protons.  Since an electron's weight is negligible, the "atomic weight" of carbon 12 is 12 au [and that's where the "12" in the name comes from]) so one mole of carbon 12 weighs 12 grams.  A methane molecule is made from one carbon atom and four hydrogen atoms.  Since we don't want to worry about isotopes here we take the average atomic weight of all isotopes of carbon, 12..011 au, and the average weight of all isotopes of hydrogen, 1.008 au, which makes the atomic weight of methane 12.011+ 4(1.008)= 16.043 au.  One mole of methane has mass 16.043 grams.

[kratious]

Yes, my other professor did. What is confusing me is finding the empirical formula. The reason  I'm asking about the mass because the percentage I get from the tin and oxide doesn't add up to 100. She taught us that to get the empirical formula you need to use the % of the molecules that equal 100%. 

     Mass of Tin Oxide: 1.249g

      Mass of Sn: 0.99g

      Mass of O: 0.259g

                    Sn- 0.99gSn X (1molSn/118.71gSn)= 0.008339 molSn

                     O- 0.259gO X (1mol Sn/ 16gO)= 0.0161875molO

Now it's asking, "Express the compounds empirical formula as Sn1Ox, where x is expressed to 3 significant figures, e.g., SnO2.34. Round x to the nearest integer. Calculate the % error of x from the integer." 

    This is what I got:

             I was finding the percent by dividing the mol i got by the mol total of SnOx. ....... That's totally wrong. Wait I think I figured it out but I'm too lazy to erase and rewrite sorry maybe this is it? :

      0.008339 mol Sn

      0.0161875 mol O      I would then divide each by the smaller mol so, 0.008339

     Sn1 O1.941179998  so O would be 2 correct? So the empirical formula is SnO2      Is it right or am I headed in the right direction? 

 

[John Cuthber]

1 minute ago, kratious said:

Is it right or am I headed in the right direction? 

Headed in the right direction.

23 hours ago, kratious said:

where x is expressed to 3 significant figures, e.g., SnO2.34

 

[kratious]

So express it as SnO1.94 ? 

[John Cuthber]