When hydrochloric acid is poured over potassium sulfide, 42.9 mL of hydrogen sulfide gas is prod

When hydrochloric acid is poured over potassium sulfide,...

When hydrochloric acid is poured over potassium sulfide, $42.9 \mathrm{mL}$ of hydrogen sulfide gas is produced at a pressure of 752 torr and a temperature of $25.8^{\circ} \mathrm{C}$. Write an equation for the gas evolution reaction and determine how much potassium sulfide (in grams) reacted.

Key Concepts

Stoichiometry

Stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. In the context of a gas evolution reaction, stoichiometry is used to determine the amount of reactant consumed based on the moles of gas produced. This process requires the balanced chemical equation to establish the mole-to-mole conversion factors between reactants and products.

Molar Mass

Molar mass is the mass of one mole of a substance and is used to convert between the number of moles and the mass in grams. In stoichiometric calculations, once the number of moles of a reactant or product is determined (for example, from gas volume using the ideal gas law), the molar mass is used to calculate the actual mass of the substance involved in the reaction.

Ideal Gas Law

The ideal gas law (PV = nRT) is a fundamental equation in chemistry that relates the pressure (P), volume (V), temperature (T), and moles (n) of a gas using the ideal gas constant (R). It is used to calculate the amount of gas present from given conditions, which is especially useful in gas evolution reactions where the volume of a gas produced can be related back to the number of moles and thus to the amount of a reacting substance.

Balanced Chemical Equations

Writing balanced chemical equations is essential for accurately representing reactions, ensuring that the law of conservation of mass is obeyed. Balancing the equation for a gas evolution reaction involves ensuring that the number of atoms for each element is equal on both sides of the reaction, which provides the correct stoichiometric relationships required for further calculations.

Transcript

00:04 In this question, we have hydrochloric acid reacting with potassium sulfide, and we're told that 42 .9 millimeters of hydrogen sulfide gas is produced at 752 tor and 258 degrees celsius.

00:19 And we're asked to write an equation for the gas evolution reaction and then determine how much potassium sulfide in grams reacted.

00:26 So the equation, we had hydrochloric acid, so hcl, reacting with potassium sulfide.

00:35 So k2s, and that is forming hydrogen sulfide gas, and it's also going to form kcl.

00:47 So then if we balance this equation, we're going to need two hcls to account for these two hydrogens, which means that we need two kcls.

00:56 So there's our balanced equation, and then we're going to figure out how much potassium sulfide in grams reacted to form this much hydrogen sulfate.

01:06 Sulfide gas.

01:08 So the first thing i'm going to do is find out how many moles of hydrogen sulfide gas are in this quantity that we're given.

01:15 And to do that, i need all of my units to be correct to use in the ideal gas equation.

01:21 So my volume needs to be in liters.

01:22 So to get to liters, i will divide by 1 ,000 and i'll have 0 .0429 liters.

01:29 My pressure needs to be in atmospheres.

01:31 To get from toward atmospheres, i'll divide by 760.

01:34 So i have 1 .02.

01:37 Atmospheres and my temperature needs to be in kelvin...