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How'd you work out this molar mass? :( watch

1. Phosphorus(V) oxide is used as a desiccating agent to remove water because of the
reaction shown below.
P4O10 + 6H2O 4H3PO4
(i) Calculate the molar mass (g mol–1) of phosphorus(V) oxide. [1]

For q (i) I added up the Ar's is P4010 (15x4)+(16x10) = 220 gmol-1

however this was incorrect and I'm really confused. Though molar mass was same as Mr but with different units? (correct answer was apparently 284 g mol-1)

2. (Original post by Lid-the-squid)
Phosphorus(V) oxide is used as a desiccating agent to remove water because of the
reaction shown below.
P4O10 + 6H2O 4H3PO4
(i) Calculate the molar mass (g mol–1) of phosphorus(V) oxide. [1]

For q (i) I added up the Ar's is P4010 (15x4)+(16x10) = 220 gmol-1

however this was incorrect and I'm really confused. Though molar mass was same as Mr but with different units? (correct answer was apparently 284 g mol-1)

I think it's because for Phosphorous you've used the proton number instead of the mass number? So it should be (31x4) + (16x10) which is 284.
3. (Original post by Pixie-x)
I think it's because for Phosphorous you've used the proton number instead of the mass number? So it should be (31x4) + (16x10) which is 284.
oh yeah oh man woops thank you ahaha

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