# Chemistry

22mL of hydrogen was collected over wter at 19C and 745mmHg. What mass of magnesium is reacted (1:1 mole ratio)

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1. 1:1 ratio for what?
Mg + 2HCl ==> H2 + Mg.

Use PV = nRT and solve for n = number of mols at the conditions listed.
For P you want dry H2 and not wet H2 (it was collected over H2O and will be wet).
Ptotal = 745
pH2O = look up vapor pressure H2O at 19C.
Pdry H2 gas = 745-vapor pressure H2O = ?
Convert P to atmospheres.
Convert T to kelvin.
Convert mL to L.
Solve for n = mols H2.
That is mols Mg also.
Then mols Mg = grams/atomic mass. You know atomic mass and mols, solve for grams.

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