:D asked in Science & MathematicsChemistry · 1 decade ago

Stoichiometric mass to mass conversions?

LOOK at numbers 74 and 75 on the link I have no idea how to do them and I need them for homework I've been trying for the past 20 minutes are so esp 74 please help!!! :O

http://classjump.com/shermanschemistrysite/documen...

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  • ?
    Lv 6
    1 decade ago
    Favorite Answer

    74.

    a.

    Steps:

    1.Determine the number of moles of 25.0 grams NaCN using its molar mass.

    1 mole NaCN = 49.0073 grams NaCN

    25.0 grams NaCN x (1 mole NaCN/49.0073 grams NaCN) = 0.510 moles NaCN

    2. Determine the number of moles Au that will reacts with this moles NaCN.

    Note: 4 moles Au reacts with 8 moles NaCN (from the balanced chemical equation)

    0.510 moles NaCN x (4 moles Au/8 moles NaCN) = 0.255 moles Au

    3. Convert moles Au to grams Au using its atomic mass.

    Note: 1 mole Au = 196.9666 grams Au

    0.255 moles Au x (196.9666 grams Au/1 mole Au) = 50.2 grams Au

    b.

    % Au = mass of Au/mass of sample x 100%

    % Au = 50.2 grams/150.0 grams x 100% = 33%

    75.

    Steps:

    1. Convert 0.275 grams AgBr to moles AgBr

    Note: 1 mole AgBr = 187.7723 grams AgBr

    0.275 grams AgBr x (1 mole AgBr/187.7723 grams AgBr) = 0.00146 mole AgBr

    2. Determine the number of moles Na3Ag(S2O3)2 produced from this mole AgBr.

    Note: 1 mole AgBr produces 1 mole Na3Ag(S2O3)2

    0.00146 mole AgBr x (1 mole Na3Ag(S2O3)2/1 mole AgBr) = 0.00146 mole Na3Ag(S2O3)2

    3. Convert to grams Na3Ag(S2O3)2

    Note: 1 mole Na3Ag(S2O3)2 = 401.0961 grams Na3Ag(S2O3)2

    0.00146 mole Na3Ag(S2O3)2 x (401.0961 grams Na3Ag(S2O3)2/1 mole Na3Ag(S2O3)2) = 0.586 grams Na3Ag(S2O3)2

    That's it!n_n

  • 5 years ago

    The easiest way to try this is to write down it out four three mol O2 4 1 mol clear up for that to get O2 in grams, than divide with the aid of the molar mass to get moles

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