Answer:
55.5 g/mol
Explanation:
When the compound dissociates it forms :
XBr₃ → X⁺ + 3Br⁻
So, 1 mol of the metal is equivalent to 3 mol of Br.
1 mol of X --------------------- 3 mol of Br
y -------------------- 4.806x10⁻² mol
By a simple direct three rule:
3y = 4.806x10⁻²
y = 1.602x10⁻² mol of X
The mass of Br in the compound is the number of moles multiplied by its atomic mass, which is 80 g/mol
m = 80x4.806x10⁻² =
m = 3.845 g
So, the mass of the metal is the total mass less the Br mass (Lavoiser's law):
mX = 4.735 - 3.845
mX = 0.890 g
The atomic mass of X is the mass dividied by the number of moles:
M = 0.890/(1.602x10⁻² )
M = 55.5 g/mol
The atomic mass of the unknown metal would be 55.87 g
Recall that: mole = mass/molar mass
Moles of Br in 4.735 g of sample = 0.04806 moles
Molar mass of Br = 79.9
Mass of Br = moles x molar mass
= 0.04806x 79.9
= 3.84 g
Mass of X = 4.735 - 3.84
= 0.895 g
In the compound XBr3, every 3 moles of Br requires 1 mole of X. Thus, if 0.04806 mole of Br is present in 4.735 g, the mole of X present would be:
0.04806/3 = 0.01602 moles
Molar mass = mass/mole
= 0.895/0.01602
= 55.87 g
More on molar mass can be found here: https://brainly.com/question/12127540?referrer=searchResults
