Yellow Zinc

Chem Questions?

Zinc metal reacts with yellow crystals of sulfur in a fiery reaction to produce a white powder of zinc sulfide. A chemist determines that 65.4 g of zinc reacts with 32.1 g of sulfur. How many grams of zinc sulfide could be produced from 11.0 g of zinc metal?

Sodium metal reacts vigorously with water. A piece of sodium weighing 20.23 g was added to a beaker containing 126.22 g of water. During reaction, hydrogen gas was produced and bubbled from the solution. The solution, containing sodium hydroxide, weighed 145.56 g. How many grams of hydrogen gas were produced?

When a mixture of aluminum powder and iron(III) oxide is ignited, it produces molten iron and aluminum oxide. In an experiment, 5.40 g of aluminum was mixed with 18.60 g of iron(III) oxide. At the end of the reaction, the mixture contained 11.17 g of iron, 8.70 g of aluminum oxide, and an undetermined amount of unreacted iron(III) oxide. No aluminum was left. What is the mass of the iron(III) oxide?

1. Thus the chemist determined that one mole of Zinc will react with 1 mole of Sulfur.
~ Thus, number of moles of Zinc Metal = 11/65.4 = 0.168195718.
~ Number of moles of Zinc Metal = number of moles of Zinc Sulfide.
~ Mass of Zinc Sulfide = 0.168195718 x Relative molecular mass, =0.168195718 x (65.4+32.1) = 16.4g (3sf)

2. First write out the Chemical Equation:
~ 2Na (Solid) + 2H2O (Liq)= H2 (gas)+ 2NaOH (Aq)
~ Number of moles of Na = Mass/Relative Molecular Mass = 20.23/22.99 = 0.879947803.
~ Number of moles of H2O = Mass/RMM = 126.22/18 = 7.0122222222
~ 0.879947803 moles of Na will react with 0.879947803 moles of H2O. But there's too much H2O. Thus, Na is limiting reactant, as it stops the H2O from being completely reacted..
~ Number of moles of H2 gas = 0.879947803/2 = 0.439973901.
~ Mass of H2 gas produced = moles x RMM = 0.439973901 x 2 = 0.879947803g = 0.880g (3sf)

3. First write out the Chemical Equation
~ 2Al + Fe2O3 = Al2O3 +2Fe
~ Limiting reactant is Aluminium, as it prevented the Iron(III) Oxide from fully reacting.
~ Number of Moles of Al = Mass/RMM = 5.4/27 = 0.2
~ 0.2 Moles of Al will react with 0.1 moles of Fe2O3
~ Mass of reacted Fe2O3 = Moles x RMM =0.1 x 159.7 = 15.97g
~Mass of unreacted Iron (III) Oxide = 18.60g - 15.97g = 2.63g.

Good Luck,
Pardon me if there's error in calculations.
Vin.

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