Zinc and magnesium metal each reacts with hydrochloric acid to make chloride salts of the respective metals, and hydrogen gas. a
11.20-g mixture of zinc and magnesium produces 0.6854 g of hydrogen gas upon being mixed with an excess of hydrochloric acid. determine the percent magnesium by mass in the original mixture.
Total mass = 11.20 g mass of H₂ = 0.6854 g molar mass of H₂ = 2.016 g/mol molar mass of Mg = 24.305 g/mol molar mass of Zn = 65.39 g/mol w-?
mass of Mg = wm mass of Zn = (1-w)m
Zn + 2HCl → ZnCl₂ + H₂ mass of H₂, m₁ = (molar mass of H₂ * mass of Zn) / molar mass of Zn = molar mass of H₂ * (1-w) * m / molar mass of Zn
Mg + 2HCl → MgCl₂ + H₂ mass of H₂, m₂ = (molar mass of H₂ * mass of Mg) / molar mass of Mg = molar mass of H₂ * wm / molar mass of Mg
Total mass of H₂ = m₁ + m₂ mass of H₂ = molar mass of H₂ * (1-w) * m / molar mass of Zn + molar mass of H₂ * wm / molar mass of Mg = molar mass of H₂ * {(1-w)/molar mass of Zn + w/molar mass of Mg}
mass of H₂ = molar mass of H₂ * {(1-w)/molar mass of Zn + w/molar mass of Mg}
{(1-w)/molar mass of Zn + w/molar mass of Mg} = mass of H₂ / (molar mass of H₂ * m)
1/molar mass of Zn - w/molar mass of Zn + w/molar mass of Mg = mass of H₂ / (molar mass of H₂ * m)
w * (1/molar mass of Mg - 1/molar mass of Zn) = mass of H₂ / (molar mass of H₂ * m) - 1/molar mass of Zn
w = [mass of H₂ / (molar mass of H₂ * m) - 1/molar mass of Zn] / (1/molar mass of Mg - 1/molar mass of Zn)
Given that camphor is a sublime material while sand is not, a gradual heating of the mixture allows for the separation of camphor from sand. The camphor vapors can then be collected and allowed to cool. This process will result in the formation of solid camphor crystals.
The energy released results in a kinetic energy of 92.2 keV for the products. We should convert keV into Joules, noting that 1 keV equals a kiloelectron volt. The required conversion is: 1.602×10⁻¹⁹ <span>joule = 1 eV
Next, we can determine the velocity of each He atom from the kinetic energy: KE = 1/2*mv² 5.76×10²³ Joules = 1/2*(4)(v²) This solves to give us: v = 5.367×10¹¹ m/s
