Al, Si, Mg
All other elements seem more necessary in life
Answer:
A)Mass of gallium plated out is 0.3440 grams
B) For 0.67 hours current of 5.79 A must to be applied to plate out 8.70 g of tin.
Explanation:
To calculate the total charge, we use the equation:

where,
C = Charge
I = Current in time t (seconds)
To calculate the moles of electrons, we use the equation:

where,
F = Faraday's constant = 96500
A) The equation for the deposition of Ga(s) from Ga(III) solution follows:

I = 0.790 A, t = 30.0 min = 1800 seconds


Moles of electron transferred:

Now, to calculate the moles of gallium, we use the equation:

n = number of electrons transferred = 3

Mass of 0.004913 moles of gallium = 0.004913 mol × 70 g/mol=0.3440 g
B) The equation for the deposition of Sn(s) from Sn(II) solution follows:

Moles of tin = 
n = number of electrons transferred = 2

Moles of electron = 

Charge transferred during time t :


Current applied for t time = I = 5.79 A

For 0.67 hours current of 5.79 A must to be applied to plate out 8.70 g of tin.
1) Reaction: 3Mg + N₂ → Mg₃N₂.
m(Mg) = 0,225 g
n(Mg) = 0,225 g ÷ 24,3 g/mol = 0,009 mol.
n(Mg) : n(N₂) = 3 : 1
n₁(N₂) = 0,003 mol.
n₂(N₂) = 0,5331 ÷ 28 = 0,019 mol.
n₃(N₂) = 0,019 mol - 0,003 mol = 0,016, m(N₂) = 0,016mol·28g/mol=0,4467g.
or simpler: m(N₂) = 0,225 g + 0,5331 - 0,3114 g = 0,4467 g.
2) Answer is: 6 <span>of fluorine atoms are combined with one uranium atom.
</span>m(U) = 209 g.
m(F) = 100 g.
n(U) = m(U) ÷ M(U)
n(U) = 209 g ÷ 238 g/mol.
n(U) = 0,878 mol.
n(F) = m(F) ÷ M(F)
n(F) = 5,263 mol
n(U) : n(F) = 0,878 mol : 5,263 mol /:0,878.
n(U) : n(F) = 1 : 6.
n - amount of substance
I think the answer is magnetic field?
volume of Ni = 25 nL = 25 x 10⁻⁹ L
mol Ni = 25 x 10⁻⁹ L x 1.25 mol/L = 3.125 x 10⁻⁸
mass = mol x Ar Ni
mass = 3.125 x 10⁻⁸ x 59 g/mol
mass = 1.84 x 10⁻⁶ g = 1.84 μg