[Freshman]

Hi, I have a few questions from my Chem class, I'd love it if anyone could help. +rep and thanks in advance.

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   Alpha-linolenic acid is one of a large group of fatty acids that are found in fish oil, walnuts and canola seeds. These nutrients are essential for good health. All of these fatty acids consist of an unsaturated hydrocarbon that is terminated by a carboxylic acid functional group. When a 6.4872 g sample of unknown fatty acid is burned in oxygen, the process consumes 14.72 g of O2. The reaction produces 17.604 g of CO2 and 3.6032 g of H2O. Based on these results and the molar masses of H (1.008 g), C (12.01 g) and O (16.00 g), how many hydrogen atoms are in each formula unit of the acid, CxHyO2? (What is the value of y?)

.    Sucrose (C12H22O11) can be mixed with potassium nitrate to form an amateur rocket propellant called rocket candy, which, despite its name, is at least mildly toxic. The properly balanced mixture reacts to form K2CO3, N2, H2O and CO2. Write the balanced reaction and determine the mass of KNO3 that should be mixed with 1.1 g of sugar to produce optimally balanced rocket candy.

Acid rain is caused in part by burning coal that contains sulfur impurities. The sulfur is converted first to SO2, which reacts with oxygen and atmospheric moisture to produce sulfuric acid, H2SO4. If a particular coal contains 2.25% sulfur (by mass), calculate the mass of sulfuric acid produced by burning a metric ton (1000 kg) of the coal.

Elemental analysis of a 3.74 mg sample of unknown hydrocarbon shows that it contains 3.202438 mg of carbon. If the molecular formula is C6Hx, what is the value of x?

4.34 g of N2O reacts completely with an equimolar amount of NO2 to form elemental nitrogen and oxygen. How much N2 is formed in this process?

   When heated, a 2.2 g sample of ammonium perchlorate, NH4ClO4 ignites and burns in the absence of any other material to produce N2, HCl, H2O and O2. Write the balanced chemical equation for this process and determine the mass of H2O produced.

How many atoms are contained in a block of aluminum metal measuring 5 mm x 7 mm x 14 mm? The density of aluminum is 2.7 g/cm3.

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A short explanation and the answer would be amazing!

[Arkcon]

Can you try to do a little bit of at least one of these diverse problems?  For a start, look at number 2.  It mentions word for reactants, and chemical formulas for products.  You can't solve it that way.  Can you convert to a balanced chemical equation?  At least begin to express the components of "rocket candy" as chemical formulas.  So you can begin to compare quantities of reactants.

[Freshman]

Fine, here we go:

Alpha-linolenic acid is one of a large group of fatty acids that are found in fish oil, walnuts and canola seeds. These nutrients are essential for good health. All of these fatty acids consist of an unsaturated hydrocarbon that is terminated by a carboxylic acid functional group. When a 6.4872 g sample of unknown fatty acid is burned in oxygen, the process consumes 14.72 g of O2. The reaction produces 17.604 g of CO2 and 3.6032 g of H2O. Based on these results and the molar masses of H (1.008 g), C (12.01 g) and O (16.00 g), how many hydrogen atoms are in each formula unit of the acid, CxHyO2? (What is the value of y?)

The fatty acid reacts with an excess of O2, consuming 14.72g O2. It produces 17.604g CO2 + 3.6032g H20.

So CxHyO2 + 14.72g O2 = 17.604g CO2 + 3.6032g H20 is where I got stuck. Is that equation even correct?

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Sucrose (C12H22O11) can be mixed with potassium nitrate to form an amateur rocket propellant called rocket candy, which, despite its name, is at least mildly toxic. The properly balanced mixture reacts to form K2CO3, N2, H2O and CO2. Write the balanced reaction and determine the mass of KNO3 that should be mixed with 1.1 g of sugar to produce optimally balanced rocket candy.

I can't even balance this equation, it gets so complicated. This problem is the one where I'm completely stuck at.

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Acid rain is caused in part by burning coal that contains sulfur impurities. The sulfur is converted first to SO2, which reacts with oxygen and atmospheric moisture to produce sulfuric acid, H2SO4. If a particular coal contains 2.25% sulfur (by mass), calculate the mass of sulfuric acid produced by burning a metric ton (1000 kg) of the coal.

SO2 + H2O (atmospheric moisture) -> H2SO4. Once again, I tried balancing and I just can't seem to do it. Even if I did balance it, I'm not sure what the step after is.

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Elemental analysis of a 3.74 mg sample of unknown hydrocarbon shows that it contains 3.202438 mg of carbon. If the molecular formula is C6Hx, what is the value of x?

I calculated the ratio of C:H to be 1:5.97, but then no matter what I tried to do, I couldn't get the answer. I figured it'd be C6H6, but that didn't work. Not sure where to progress from this.

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How many atoms are contained in a block of aluminum metal measuring 5 mm x 7 mm x 14 mm? The density of aluminum is 2.7 g/cm3.

I got 290mm which would be 29cm3 x 2.7g. The next logical step would be to multiply by Avogadro's number to get 5.996x10^23, but that's the wrong answer apparently.

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When heated, a 2.2 g sample of ammonium perchlorate, NH4ClO4 ignites and burns in the absence of any other material to produce N2, HCl, H2O and O2. Write the balanced chemical equation for this process and determine the mass of H2O produced.

I balanced this out to 4NH4ClO4 --> 2N2 + 4HCl + 6H2O + 5O2, with 6 moles of H2O being equal to 132.36g. 2.2g of 57.543g (weight of ammonium perchlorate) gives .038 of a mole, which I figured would give me the answer when multiplied by 132.36, but it didn't. So a step by step process here would be really appreciated.

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4.34 g of N2O reacts completely with an equimolar amount of NO2 to form elemental nitrogen and oxygen. How much N2 is formed in this process?

2N2O + 2NO2 -> 3N2 + 3O2? Yet again, another question that completely stumps me. No clue what to do with the 4.34g of N2O, much less how to figure out how much N2 is formed.

[Arkcon]

OK, we can't possibly answer every question, completely, in one thread.  It tried to make you pick one, so we could teach you the basic concepts, and apply them to each problem on your own.  So lets go ...

4.34 g of N2O reacts completely with an equimolar amount of NO2 to form elemental nitrogen and oxygen. How much N2 is formed in this process?

2N2O + 2NO2 -> 3N2 + 3O2? Yet again, another question that completely stumps me. No clue what to do with the 4.34g of N2O, much less how to figure out how much N2 is formed.

That one is balanced properly.  So you now have a balanced chemical equation.  Problem is, this equation uses the units of moles, and you're given grams of reactant, and you need grams or product, you now have to convert back and forth.

They're all pretty much the same.  Just conversions from one set of units to another.  Some of the others are a little bit tougher, so I started with this one.

[AWK]

Sucrose (C12H22O11) can be mixed with potassium nitrate to form an amateur rocket propellant called rocket candy, which, despite its name, is at least mildly toxic. The properly balanced mixture reacts to form K2CO3, N2, H2O and CO2. Write the balanced reaction and determine the mass of KNO3 that should be mixed with 1.1 g of sugar to produce optimally balanced rocket candy.

I can't even balance this equation, it gets so complicated. This problem is the one where I'm completely stuck at.

Then use internet balancer.

[Freshman]

OK, we can't possibly answer every question, completely, in one thread.  It tried to make you pick one, so we could teach you the basic concepts, and apply them to each problem on your own.  So lets go ...

4.34 g of N2O reacts completely with an equimolar amount of NO2 to form elemental nitrogen and oxygen. How much N2 is formed in this process?

2N2O + 2NO2 -> 3N2 + 3O2? Yet again, another question that completely stumps me. No clue what to do with the 4.34g of N2O, much less how to figure out how much N2 is formed.

That one is balanced properly.  So you now have a balanced chemical equation.  Problem is, this equation uses the units of moles, and you're given grams of reactant, and you need grams or product, you now have to convert back and forth.

They're all pretty much the same.  Just conversions from one set of units to another.  Some of the others are a little bit tougher, so I started with this one.

I'm still not fully understanding how to do it. Can you please give me a simple step by step process?


Also, thanks for the internet balancer.

[Arkcon]

OK.  How many moles of N₂O is 4.34 grams?  How many moles of N₂ is one mole of N₂O ( as given by your balanced equation, I know they're different compounds, but your equation says that N2O equals N2, at least after the reaction is done ... equation ... equals... you see)  How many moles of N₂ is whatever number of moles you calculated moles of N₂O you had based on grams.  You may be able to stop there, but I'm guessing the question wants to have amount of N₂ in grams, so how many grams N₂ is whatever moles N₂ you calculated?

I made that into a paragraph.  You can put that on paper stepwise, one sentence, and the calculations for it beneath each sentence.  You can use that as a template for other problems of this sort.

[Freshman]

Alright, I've made some progress.

   Sucrose (C12H22O11) can be mixed with potassium nitrate to form an amateur rocket propellant called rocket candy, which, despite its name, is at least mildly toxic. The properly balanced mixture reacts to form K2CO3, N2, H2O and CO2. Write the balanced reaction and determine the mass of KNO3 that should be mixed with 1.1 g of sugar to produce optimally balanced rocket candy.

I have:

5C12H22O11 + 48KNO3 -> 24K2CO3 + 24N2 + 55H2O + 36CO2, and I'm not sure where to go from here. I just can't see how to implement the 1.1g of sugar.


Also, How many atoms are contained in a block of aluminum metal measuring 5 mm x 7 mm x 14 mm? The density of aluminum is 2.7 g/cm3.

This should be 5x7x14mm = 490 mm = 49cm

49cm x 2.7 g/cm3 = 132.3g, divided by the molar mass of Al is 4.9033, which I would multiply by 6.023x10^23, yet it says that's not the right answer.


That first one is the one that really eludes me, the 2nd one should be correct, but I'm not sure why it is not.

[AWK]

_{5C12H22O11 + 48KNO3 -> 24K2CO3 + 24N2 + 55H2O + 36CO2, and I'm not sure where to go from here. I just can't see how to implement the 1.1g of sugar.}


http://www.chembuddy.com/?left=balancing-stoichiometry&right=ratio-proportions

[sjb]

Also, How many atoms are contained in a block of aluminum metal measuring 5 mm x 7 mm x 14 mm? The density of aluminum is 2.7 g/cm3.

This should be 5x7x14mm = 490 mm = 49cm

49cm x 2.7 g/cm3 = 132.3g, divided by the molar mass of Al is 4.9033, which I would multiply by 6.023x10^23, yet it says that's not the right answer.


That first one is the one that really eludes me, the 2nd one should be correct, but I'm not sure why it is not.

What are the units of volume?

[AWK]

5x7x14mm

these are cubic milimeters!

[Arkcon]

I have:

5C12H22O11 + 48KNO3 -> 24K2CO3 + 24N2 + 55H2O + 36CO2, and I'm not sure where to go from here. I just can't see how to implement the 1.1g of sugar.

OK.  5 grams of sugar is how many moles of sugar? 

If I'd asked you instead, 5 moles of sugar, you'd know exactly how many moles of KNO3

If I'd asked you to solve for 10 moles of sugar, you'd do the amount of moles of KNO3 in your head

If I'd asked for 0.372 moles of sugar, you'd curse, and break out your calculator, and tell me how many moles of KNO3

1.1 grams of sugar has a value in moles, you use the formula weight to convert.  You convert the moles of KNO3 back into grams.

Grams sugar moles sugar moles KNO3  grams KNO3