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kryton1212 Group Title

(a) What is the mass of nitrogen present in the sample of sodium nitrate (NaNO3) which contains 100g of sodium? (b) What is the mass of water of crystallization present in the sample of sodium carbonate-10-water (Ma2CO3·10H2O) which contains 4.6g of sodium? (c) A metal oxide MO contains 79.87% by mass of the metal M. Find the relative atomic mass of M. (d) 26.88g of a metal chloride MCl contains 5.68 g of chlorine. Find the relative atomic mass of the metal M.

  • one year ago
  • one year ago

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  1. kryton1212 Group Title
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    @gerryliyana

    • one year ago
  2. gerryliyana Group Title
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    (Ar Nitrogen/Mr NaNo3) x mass of NaNO3

    • one year ago
  3. kryton1212 Group Title
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    Ar stands for what?

    • one year ago
  4. gerryliyana Group Title
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    mass of relative atom

    • one year ago
  5. gerryliyana Group Title
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    Mr is "mass of relative molecule"

    • one year ago
  6. kryton1212 Group Title
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    ok

    • one year ago
  7. kryton1212 Group Title
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    no need to times 100g?

    • one year ago
  8. gerryliyana Group Title
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    do you have a periodic table?

    • one year ago
  9. kryton1212 Group Title
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    yes

    • one year ago
  10. kryton1212 Group Title
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    wait a moment

    • one year ago
  11. sirm3d Group Title
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    \[\large m \text { N}=100g \text { Na} \times \frac{ 14g \text{ N} }{ 23g \text { Na} } \approx 61g \text { N}\]

    • one year ago
  12. kryton1212 Group Title
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    Na=23.0g N=14.0g O=16.0g

    • one year ago
  13. kryton1212 Group Title
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    why 23g Na?? not NaNO3?

    • one year ago
  14. kryton1212 Group Title
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    but my idea is this... |dw:1354705910345:dw|

    • one year ago
  15. sirm3d Group Title
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    our interest is in the element Na and N in the compound. the ratio of these elements is 1:1

    • one year ago
  16. kryton1212 Group Title
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    uhhh...what do you mean?

    • one year ago
  17. sirm3d Group Title
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    the compound contains 100g of Na. it did not say the compound NaNO3 weighs 100g.

    • one year ago
  18. gerryliyana Group Title
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    yes sodium is Na.., so 100 is mass of Na

    • one year ago
  19. kryton1212 Group Title
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    @sirm3d so it depends on the question asking about the mass of something which contains how many grams of that thing, right? @gerryliyana that hundred of sodium represents what? the mass or the weight?

    • one year ago
  20. sirm3d Group Title
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    yes. be careful of the question. if the 100g is the mass of the compound NaNO3, then we need to compute the mass on Na in the compound.

    • one year ago
  21. gerryliyana Group Title
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    represent mass of Na

    • one year ago
  22. kryton1212 Group Title
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    @sirm3d okay, how about part b? @gerryliyana thanks, I got it :) part b please

    • one year ago
  23. kryton1212 Group Title
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    4.6*(10H2O/Na2) ?

    • one year ago
  24. sirm3d Group Title
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    same thing. The mass of Na in the compound, sodium carbonate decahydrate, is 23g. we compute the total mass of water molecules in the compound

    • one year ago
  25. sirm3d Group Title
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    mass of 10 moles of water is 10 x 18g = 180 g

    • one year ago
  26. sirm3d Group Title
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    we convert 4.6 g Na to g H2O by the mass ratio in the compound (180 g H2O / 23 g Na)

    • one year ago
  27. kryton1212 Group Title
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    but there are two Na atom.... Na2Co3

    • one year ago
  28. kryton1212 Group Title
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    sorry for typing mistakes, it should be Na2CO3 10H2O

    • one year ago
  29. sirm3d Group Title
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    sorry, missed that two Na. Mass of Na in compound is 46 g. use the mass ratio 180g H2O / 46g Na

    • one year ago
  30. kryton1212 Group Title
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    |dw:1354706692310:dw|

    • one year ago
  31. sirm3d Group Title
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    right.

    • one year ago
  32. kryton1212 Group Title
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    thanks. How about part c?

    • one year ago
  33. sirm3d Group Title
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    assume 100g mass of compound MO. Mass of M in 100g compound is 79.87 g, mass of O in 100g compound is 20.13 g.

    • one year ago
  34. kryton1212 Group Title
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    I got this one

    • one year ago
  35. sirm3d Group Title
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    i got 63.5g M

    • one year ago
  36. kryton1212 Group Title
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    so what is the formula about finding relative atomic mass of M?

    • one year ago
  37. kryton1212 Group Title
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    there is no answer on my textbook. I cannot ask my teacher since I will have Chemistry examination tonight.

    • one year ago
  38. sirm3d Group Title
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    it is the mass of M relative to the mass of O

    • one year ago
  39. kryton1212 Group Title
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    there are 1 atom of M, right?

    • one year ago
  40. sirm3d Group Title
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    yes, 1:1 ratio. so the mass of the oxygen in MO is 16g. the mass of M relative to 16g O present in the compound is the relative mass of M

    • one year ago
  41. kryton1212 Group Title
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    so M is copper....

    • one year ago
  42. kryton1212 Group Title
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    mass of M=79.87g and the relative atomic mass is ...?

    • one year ago
  43. sirm3d Group Title
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    if there is 1 mol of MO, the mass of M is 63.5 g. if there are 2 mol of MO, the mass of M is 127g. relative mass means mass in ONE mol of the compound.

    • one year ago
  44. kryton1212 Group Title
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    how can you get the answer?

    • one year ago
  45. sirm3d Group Title
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    we assumed that IF there are 100g of MO, clearly 79.77% of that mass belongs to M. you would arrive at the same result if you assume that the starting mass of MO is 20g. In this 20g MO, the mass of M is 79.87% of 20g while 20.13% of 20g is the mass of O.

    • one year ago
  46. sirm3d Group Title
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    you cannot give the actual mass of M in the compound MO if you do not have the actual mass of MO.

    • one year ago
  47. sirm3d Group Title
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    i'll give an analogy just to be clear with the "relative" mass. Suppose you got 90% of the questions in your exam, can you tell me how many correct answers you got?

    • one year ago
  48. kryton1212 Group Title
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    if there were 100 questions in my exam, I got 90 questions correct. I know why you assume 100 g be the mass of the compound MO and the ratio is 1:1 total mass =100 g mass of M=79.87 g mass of O=20.13 g relative atomic mass of O=16.0 g But I am confusing how to get the relative atomic mass of M...... I still cannot get you idea about M...

    • one year ago
  49. sirm3d Group Title
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    we convert the relative atomic mass of O = 16.0g to relative atomic mass of M using the available masses of 79.87g M and 20.13g O.

    • one year ago
  50. sirm3d Group Title
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    16.0g O x 79.87g M / 20.13g O = 63.5g M

    • one year ago
  51. kryton1212 Group Title
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    the relative atomic mass of O is known and ask for the relative atomic mass of M, we need to make the mass of O be the denominator and mass of M be the numerator. If the relative atomic mass of M is known and ask for the relative atomic mass of O, we need to make the mass of M be the denominator and mass of O be the numerator. is it?

    • one year ago
  52. sirm3d Group Title
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    yep. that's how you convert the given.

    • one year ago
  53. kryton1212 Group Title
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    thank you for correcting my concepts and I am working with part d, I will give you response when I get my answer and you check is my answer correct or not

    • one year ago
  54. sirm3d Group Title
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    |dw:1354708533879:dw| observe how i got rid of g O and change it to g M

    • one year ago
  55. kryton1212 Group Title
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    I know it is the answer of part d 168 g M?

    • one year ago
  56. kryton1212 Group Title
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    are you here?

    • one year ago
  57. sirm3d Group Title
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    1 got 132.32 g M

    • one year ago
  58. kryton1212 Group Title
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    ummm......what are your steps?

    • one year ago
  59. sirm3d Group Title
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    g M in MCl = 268.88g-5.68g=21.2g M

    • one year ago
  60. sirm3d Group Title
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    mass ratio is 21.2g M / 5.68g Cl

    • one year ago
  61. kryton1212 Group Title
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    ummmm...you get something wrong.... is 26.88g instead of 268.88g

    • one year ago
  62. sirm3d Group Title
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    sorry. typo error.

    • one year ago
  63. sirm3d Group Title
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    relative mass of Cl = 35.453g

    • one year ago
  64. kryton1212 Group Title
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    just take the relative mass of Cl =35.5g

    • one year ago
  65. sirm3d Group Title
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    35.5g Cl x 21.2g M / 5.68g Cl = 132.5g M

    • one year ago
  66. sirm3d Group Title
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    M = Cs

    • one year ago
  67. kryton1212 Group Title
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    why 21.2 g?

    • one year ago
  68. kryton1212 Group Title
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    26.88g-5.68g?

    • one year ago
  69. kryton1212 Group Title
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    okay I got it. Thank you very much. :)

    • one year ago
  70. sirm3d Group Title
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    yep. 26.88g - 5.68g = 21.2g

    • one year ago
  71. kryton1212 Group Title
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    1.200 g of a compound containing only C, H and O gave 1.173 g of CO2 and 0.240 g of H2O on complete combustion. Find the empirical formula of the compound.

    • one year ago
  72. sirm3d Group Title
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    hmm. 0.213 g O2 used in the process.

    • one year ago
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