A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • one year ago

Calculate the mass of magnesium oxide formed when 10.0 grams of Mg burns in excess oxygen

  • This Question is Closed
  1. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    do you have a balanced equation?

  2. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @jcab98

  3. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Yep Its 2Mg(s)+O2(g)=2MgO(s)

  4. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    If oxygen is excess then magnesium is the limiting reagent. I like the dimensional analysis method because you can pretty much do everything in 1 step.|dw:1436102167827:dw||dw:1436102167827:dw|

  5. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    idk why that did that twice

  6. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    if you notice, all the units cancel except g MgO and all you have to do is multiply and divide the numbers |dw:1436102693078:dw|

  7. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @peachpi could you describe the method you used for the above answer because this method isnew to me

  8. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Dimensional analysis is where you treat the parts of a chemical equation as units that you can convert from one form to another using the ratios in the equation. Once the equation is balanced all the compounds/elements are in a fixed ratio, so what you're essentially doing is scaling up or down depending on what you start with or want to end with. ^that seems kind of like a word salad :/ It's kind of like converting miles to cm. You could convert miles to feet first, then in another step feet to inches, then in another inches to cm. Or you could set it all up once as a series of ratios to be multiplied Does that make sense?

  9. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @peachpi so what did you do to start off.Idont understand how you got the numbers on the top and the bottom

  10. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I debated whether putting them in vs having you fill them in...especially since we might be using different periodic tables. The 24.31is the molar mass of Mg. Basically molar mass is in units of g/mol. As in there are 24.31 g of Mg in 1 mole of Mg. The grams go on bottom because you want it to cancel with the 10 g given in the problem

  11. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so that leaves the 1 mol Mg to go on top

  12. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    with me so far?

  13. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes @peachpi

  14. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok. the 2's come from the coefficients of the balanced equation. After the first step we have mol Mg on top. We need to convert that to mol MgO, That's why 2 mol MgO goes on top and 2 mol Mg is on bottom. This is hands down the most important part where you're going from one chemical to another. If the equation isn't balanced it won't be right. This one works out to a 1:1 ratio, but that won't always be the case

  15. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Continue @peachpi im starting to understand now

  16. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok. you now have mol MgO. Since this problem wants grams you have to use the molar mass for MgO to change moles to grams. I got 40.31 g/mol for the molar mass, so 40.31 g MgO goes on top and 1 mol MgO goes on bottom. That's the reverse of the way we did it at the beginning of the problem when we were going from grams to moles. This time we're doing moles to grams

  17. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    g MgO is what is asked for in the problem so that's the last conversion.

  18. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    do the top part of the working out represent what you want to find out ?

  19. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes it does. and the bottom is what you have/ need to cancel

  20. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    when you mean need to cancel is that with the10.0g Mg

  21. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    FYI, See http://www.chembuddy.com/?left=balancing-stoichiometry&right=dimensional-analysis and http://www2.sunysuffolk.edu/sambass/index_files/studyguide/SA-5.pdf for more info on the method. The first link has another example, coincidentally using the same formula. The 2nd has a summary of the method in general

  22. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    or the previous step

  23. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    every step will cancel. So yes the first step is canceling the 10 g with g

  24. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Is this method only used for this type of question

  25. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    how do you mean?

  26. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    you can use it in any application where you're converting elements with a constant ratio, if that's what you mean

  27. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    For only calcualting the mass of products when given a mass of a reactant

  28. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    What other applications are there

  29. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    no you can actually use it for mole to mole, moles to gram, etc. Those are actually a little shorter than this one. If you had 10 mole of Mg and wanted to find g MgO for example, you wouldn't need to do that first conversion with the molar mass. You'd start with 10 mol Mg then jump straight to the ratios from the equation. Similar thing if you had moles Mg and wanted moles MgO. That middle conversion would be the only step.

  30. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    As for other applications, I used it a lot in physics like when finding speeds given rotation or converting between english/metric units for mass and force

  31. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Thank you for your help @peachpi .For my first question on this site the information you provided me will really help me in my chemistry studies. Btw What country are you from and what grade are you in

  32. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    you're welcome! happy to help. I'm from the Bahamas and I've been out of school a loooong time. I tutor so I just come on to keep my brain fresh.

  33. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Well thank you for your help and your time.I'm currrently in Year 11 Studying Chemistry for the first time in Australia .Not doing that badly at it ,coming 2nd in the grade.I'm just revising over calculations for chemistry, because its a hard concept to grasp

  34. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    You're welcome. Good luck to you. It's a fascinating subject.

  35. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.