Question

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Is the percent mass basically (element)/(compound) times 100?

Answer 1

basically yes, but you still have to do some stoichiometry to find the mass of \(iron\) that produced that mass of hydrogen gas.

Answer 2

Stoichometry? Like balancing the equation o:

Answer 3

@NvidiaIntely I'm working on chemistry, I just left this page up so I can get any help sorry.

Answer 4

my previous answer was wrong here it is better

moles H2 = 0.100 g / 2.016 g/mol=0.0496
let x = mass Fe
let y = mass Al

x + y = 1.99 => x =1.99-y

x / 55.847 + (3/2) (y / 26.9815) = 0.0496

0.0179 x + 0.05559 y = 0.0496

replace x for x=1.99-y to have the equation with only one variable "y" and solve for "y"

0.0179 (1.99-y) + 0.05559 y = 0.0496
0.035621- 0.0179 y + 0.05559 y = 0.0496
0.03769 y = 0.0496 - 0.035621

y = 0.013979/0.03769 = 0.371 g Al = 18.64 % Al
x= 1.99-0.371= 1.619g Fe = 81.36 % Fe
------------------------------
1.619 /55.847 = 0.02899 mol Fe = 0.02899 moles H2
0.371/26.981 = 0.01375 mol Al = 0.01375 (3/2)= 0.02063 moles H2

0.02899 moles H2 + 0.02063 moles H2 = 0.0496 mol H2