Question

Given the balanced equation below, calculate the moles of aluminum that are needed to react completely with 17.5 moles of FeO? You must show all of your work.

2Al + 3FeO à 3Fe +Al2O3

Sodium and water react according to the following equation. If 51.5g of sodium are added to excess water, how many liters of hydrogen gas are formed at STP? Show all work for credit.

2Na + 2H2O à 2NaOH + H2

Answer 1

Question 1

The moles off Al that are needed to react completely with 17.5 moles of FeO is 11.67 moles

calculation

2Al + 3 FeO→ 3 Fe + Al₂O₃

From equation above Al: FeO is 2:3

therefore the moles of Al = 17.5 moles x 2 /3 = 11.67 moles

Question 2

The number of liters of hydrogen gas that are formed at STP 25.088 L

calculation

2Na + 2H₂O → NaOH +H₂

Step 1 : calculate the moles of Na

moles = mass÷ molar mass

from the periodic table the molar mass of Na = 23 g/mol

moles= 51.5 g÷ 23 g/mol =2.24 moles

Step 2: use the mole ratio to determine the moles of H₂

Na:H₂ is 2:1 therefore the moles of H₂ = 2.24 moles x 1/2 =1.12 moles

Step 3: calculate the number of liters of H₂ at STP

that is at STP 1 mole of a gas = 22.4 L

1.12 moles = ? L

by cross multiplication

=( 1.12 moles x 22.4 L) / 1 mole = 25.088 L