Answer:
mass of Helium = mole of Helium x Molarmass of Helium
Explanation:
Mole of Helium = volume of Helium/ 22.4dm^3/mol
= 7.00 x 10^2/22.4
= 31.25mol
Mass of Helium = mole of Helium x Molarmass of Helium
= 31.25mol x 4g/mol
= 125g
Answer:
(a) oxygen
(b) 154g (to 3sf)
(c) 79.9% (to 3sf)
Explanation:
mass (g) = moles × Mr/Ar
note: eqn means chemical equation
(a)
moles of P = 84.1 ÷ 30.973 = 2.7152 moles
moles of O2 = 85÷2(16) = 2.65625 moles
Assuming all the moles of P is used up,
moles of O2 / moles of phosphorus = 5/4 (according to balanced chemical eqn)
moles of O2 required = 5/4 × 2.7152moles = 3.394 moles (more than supplied which is 2.65625moles)
therefore there is insufficient moles of O2 and the limiting reactant is oxygen.
(b)
moles of P2O5 produced
= 2/5 (according to eqn) × 2.7152
= 1.08608moles
mass of P2O5 produced
= 1.08608 × [ 2(30.973) + 5(16) ]
= 154.164g
= approx. 154g to 3 sig. fig.
(c)
% yield = actual/theoretical yield × 100%
= 123/154 × 100%
= 79.870%
= approx. 79.9% (to 3sf)
True- the finches would eat different sizes nuts and seeds as they would occupy different niches over times which lead to differences in beak sizes within the island
Answer:
Mass = 7.2 g
Explanation:
Given data:
Mass of ZnO = 36.9 g
Mass of oxygen needed = ?
Solution:
Chemical equation:
2Zn + O₂ → 2ZnO
Number of moles of ZnO:
Number of moles = Mass/ molar mass
Number of moles = 36.9 g/81.38 g/mol
Number of moles = 0.45 mol
Now we will compare the moles of ZnO with oxygen:
ZnO : O₂
2 : 1
0.45 : 1/2 × 0.45 = 0.225
Mass of oxygen:
Mass = number of moles × molar mass
Mass = 0.225 mol × 32 g/mol
Mass = 7.2 g
