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Which metal is it (gas law)?
If a 100.0 mg sample of this metal reacts with excess acid to produce 14.55 mL of hydrogen gas (H2) measured at 735 torr and 20°C, is the Rubidium, Strontium, or Yttrium?
1 Answer
- HarleyLv 58 years agoFavorite Answer
Moles hydrogen gas:
PV = nRT
n = PV/RT
n = (735 torr x 1 atm/760 torr)(0.01455L)/(0.0821 L-atm/mol-K)(20 + 273K)
n = 5.85 x 10^-4 moles
Molar mass M: 0.100g/5.85 x 10^-4 moles = 170.94g/mol
But neither metal above matches this.
But dividing it by 2 will get 85.47g/mol, which fits Rubidium
2Rb + 2HCl --> 2RbCl + H2
This is the chemical equation
if Rb were to react with an acid.
Molar ratio Rb to H2 is 2:1
so moles Rb = 5.85x10^-4 * 2 = 0.00117 mol
Molar mass metal: 0.100g/ 0.00117mol = 85.47g/mol
The element that fits this molar mass is Rubidium
