I am a freshman in college, and am taking a placement test soon, but haven't seen chemistry since 10th grade.
I'd appreciate any help I can get from anyone here to help me solve this problem:
Hydrogen and sulfur chemically combine to form the gas hydrogen sulfide, according to the reaction: H2 (g) + S(s) → H2S(g). How many liters of hydrogen are required to form 7.4 L of hydrogen sulfide (at STP: 273 K, 101.3 kPa)?
I know that it involves stoichiometry, and the Ideal Gas Law, but am kind of confused on how to start it.
Thank you in advance!
Your equation is balanced as written.
It tells you that the number of H2S moles formed equals the number of H2 moles reacted. Since you have defined the temperature and pressure of reactants and product to be the same, the number of liters of H2 and H2S are also the same.
The answer is 7.4 Liters. You do not have to use the gas law.
To solve this problem, you can use stoichiometry and the ideal gas law. Here are the steps to solve it:
1. Write and balance the chemical equation: H2 (g) + S(s) → H2S(g). The coefficients in front of the substances represent the mole ratio between them.
2. Determine the molar ratio between hydrogen and hydrogen sulfide from the balanced equation. In this case, the ratio is 1:1, meaning one mole of hydrogen reacts with one mole of hydrogen sulfide.
3. Use the ideal gas law, which is PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant (0.0821 L•atm/(mol•K)), and T is temperature in Kelvin.
4. Convert the given volume of hydrogen sulfide to moles. Since the volume is given at STP (standard temperature and pressure), you can use the molar volume of a gas at STP, which is 22.4 L/mol.
Moles of H2S = volume of H2S (in L) / 22.4 L/mol
5. Use the mole ratio from step 2 to determine the number of moles of hydrogen gas needed to react.
Moles of H2 = Moles of H2S (from step 4) x mole ratio
6. Use the ideal gas law to calculate the volume of hydrogen gas in liters.
V = (n x R x T) / P
Here, n is the number of moles of hydrogen, R is the ideal gas constant, T is the temperature in Kelvin (273 K), and P is the pressure (101.3 kPa).
7. Substitute the values into the equation from step 6 and solve for V. This will give you the volume of hydrogen gas required in liters.
Remember to use the correct units and conversions throughout the calculations.