Use the reaction to calculate the mass of iron that must be used to obtain 0.500L of hydrogen at STP.

Question

3Fe(s)+4H2O(I)->Fe3O4(s)+4H2(g)

Answer 1

First, we need to determine the number of moles of hydrogen gas (H2) produced:

From the balanced chemical equation, we can see that 3 moles of iron (Fe) react with 4 moles of water (H2O) to produce 4 moles of hydrogen gas (H2). Therefore, the mole ratio of Fe to H2 is 3:4.

Since the volume of gas is given at STP (Standard Temperature and Pressure), we can use the ideal gas law to calculate the number of moles of hydrogen gas produced:
PV = nRT

Where:
P = Pressure = 1 atm
V = Volume = 0.500 L
n = Number of moles
R = Ideal gas constant = 0.0821 L.atm/mol.K
T = Temperature in Kelvin = 273 K

n = PV/RT
n = (1 atm * 0.500 L)/(0.0821 L.atm/mol.K * 273 K)
n ≈ 0.0229 moles

Now, using the mole ratio from the balanced chemical equation:
3 moles of Fe produce 4 moles of H2
x moles of Fe produce 0.0229 moles of H2

x = (0.0229 moles * 3 moles)/(4 moles)
x ≈ 0.0172 moles

Finally, we can calculate the mass of iron needed using the molar mass of iron (Fe) which is approximately 55.85 g/mol:
Mass = moles * molar mass
Mass = 0.0172 moles * 55.85 g/mol
Mass ≈ 0.961 g

Therefore, approximately 0.961 grams of iron must be used to obtain 0.500 L of hydrogen gas at STP.