Answer to Question #3078 in Physical Chemistry for Yasmine

Question

The equation of reaction between potassium and water.

2K + 2H[sub]2[/sub]O(1) --> 2KOH(aq) + H[sub]2 [/sub]
Find the mass of potassium needed to produce 1.505 x 10[sup]24[/sup] hydorgen molecule.

Answer 1

Let's find the amount of moles of H₂:
1.505x1024/6.022 x 10²³ = 2.5 mol.
From the ballanced equation
2K + 2H₂O(1) -> 2KOH(aq) + H₂
we can see that potassium has twice mol than H₂.
v(H₂) = 5 mol.
The mass of the potassium is 39 g/mol/ * 5 mol = 195 g.