Answer : The mass of Ni is, 80.346 g
Solution :
First we have to calculate the number of moles.
Now we have to calculate the number of atoms of 
As 1 moles contains 
number of molecules
So, 1.369 moles contains 
number of molecules
One molecule has one nitrogen atom then number of molecules of will contain number of nitrogen atoms
As per question number of Ni atoms is equal to the number of nitrogen atoms
Number of Ni atoms= atoms
Number of moles = 
Mass of Nickel = 
Molecular mass of Nickel = 58.69 g/mol
Mass of nickel = 
You need to use the Ka for the acetic acid and the equilibrium equation.
Ka = 1.85 * 10^ -5
Equilibrium reaction: CH3COOH (aq) ---> CH3COO(-) + H(+)
Ka = [CH3COO-][H+] / [CH3COOH]
Molar concentrations at equilibrium
CH3COOH CH3COO- H+
0.50 - x x x
Ka = x*x / (0.50 - x) = x^2 / (0.50 - x)
Given that Ka is << 1 => 0.50 >> x and 0.50 - x ≈ 0.50
=> Ka ≈ x^2 / 0.50
=> x^2 ≈ 0.50 * Ka = 0.50 * 1.85 * 10^ -5 = 0.925 * 10^ - 5 = 9.25 * 10 ^ - 6
=> x = √ [9.25 * 10^ -6] = 3.04 * 10^ -3 ≈ 0.0030
pH = - log [H+] = - log (x) = - log (0.0030) = 2.5
Answer: 2.5
20 B203(s) + 12180 HF(l) = 4060 BF3(g) + 609 H20(l)
Neutral atoms get smaller as you move across the periodic table from (left to right) because the atom increases in electrons. The more electrons, the bigger the effective nuclear charge (electron and proton attraction) and so basically the atom shrinks.
