K2SO4 MgSO4 Al2(SO4)3 Ge2(SO4)4
KNO3 Mg(NO3)2 Al(NO3)3 Ge(NO3)4
KCH3COO Mg(CH3COO)2 Al(CH3COO)3 Ge(CH3COO)4
Note: all of the numerical are subscript to each element or compound.
We get the pressure of the hydrogen gas from the difference between the measured pressure and the vapor pressure of water:
total pressure = Pressure of H2 + Vapor Pressure of H2O
1.00 atm = Pressure of H2 + 0.0313 atm
Pressure of H2 = 1.00 atm - 0.0313 atm = 0.9687 atm
From the ideal gas law,
PV = nRT
we can calculate for the number of moles of H2 as
n = PV/RT = (0.9687 atm)(0.246L) / (0.08206 L·atm/mol·K)(298.15 K)
= 0.00974 mol H2
where
V = 246 mL (1 L / 1000 mL) = 0.246 L
T = 25 degrees Celsius + 273.15 = 298.15 K
We use the mole ratio of Na and H2 from the reaction of sodium metal with water as shown in the equation
2Na(s) + 2H2O(l) → 2 NaOH(aq) + H2(g)
and the molar mass of sodium Na to get the mass of sodium used in the reaction:
mass of Na = 0.00974 mol H2 (2 mol Na /1 mol H2)(22.99 g Na/1 mol Na)
= 0.448 grams of sodium
Answer:
Yes, the chemist can determine which compound is in the sample.
Explanation:
In 1 mole of K₂O, the mass of K is 2 × 39.1 g = 78.2 g and the mass of K₂O is 94.2 g. The mass ratio of K to K₂O is 78.2 g / 94.2 g = 0.830.
In 1 mole of K₂O₂, the mass of K is 2 × 39.1 g = 78.2 g and the mass of K₂O₂ is 110.2 g. The mass ratio of K to K₂O₂ is 78.2 g / 110.2 g = 0.710.
If the chemist knows the mass of K and the mass of the sample, he or she must calculate the mass ratio of K to the sample.
- If the ratio is 0.830, the compound is pure K₂O.
- If the ratio is 0.710, the compound is pure K₂O₂.
- If the ratio is not 0.830 or 0.710, the sample is a mixture.