Iron reacts with hydrochloric acid to produce iron(II)...

Iron reacts with hydrochloric acid to produce iron(II) chloride and hydrogen gas: $$ \mathrm{Fe}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \longrightarrow \mathrm{Fe} \mathrm{Cl}_{2}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g}) $$ The $\mathrm{H}_{2}$ gas from the reaction of $2.2 \mathrm{g}$ of iron with excess acid is collected in a $10.0-$ I. flask at $25^{\circ} \mathrm{C}$. What is the pressure of the $\mathrm{H}_{2}$ gas in this flask?

Iron reacts with hydrochloric acid to produce iron(II) chloride and hydrogen gas:
$$
\mathrm{Fe}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \longrightarrow \mathrm{Fe} \mathrm{Cl}_{2}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})
$$
The $\mathrm{H}_{2}$ gas from the reaction of $2.2 \mathrm{g}$ of iron with excess acid is collected in a $10.0-$ I. flask at $25^{\circ} \mathrm{C}$. What is the pressure of the $\mathrm{H}_{2}$ gas in this flask?

Key Concepts

Temperature Conversion

Temperature conversion, particularly from Celsius to Kelvin, is necessary when using the Ideal Gas Law, as the equation requires the temperature in Kelvin. This is done by adding 273.15 to the temperature in degrees Celsius.

Ideal Gas Law

The Ideal Gas Law (PV = nRT) is a fundamental equation that relates the pressure, volume, temperature, and number of moles of a gas. It provides a method to calculate any one of these state variables if the others are known, assuming the gas behaves ideally.

Molar Mass

Molar mass is the mass of one mole of a substance expressed in grams per mole. It is used to convert between the mass of a substance and the number of moles, which is essential in quantitative chemical calculations.

Stoichiometry

Stoichiometry involves using the balanced chemical equation to determine the quantitative relationships between reactants and products. It allows for the conversion of mass of a substance into moles and helps determine how much product is formed from a given amount of reactant.

Transcript

00:01 We're given here the reaction between iron and the solid state plus hydrochloric acid, a solution of hydrochloric acid, and this reaction produces iron two chloride in solution plus hydrogen ion, hydrogen gas.

00:37 The volume or the flask in which the escaping gas is getting collected, in other words, the volume that hydrogen will occupy is equal to 10 liters.

01:03 The temperature at which this gas is going to be collected is going to be 25 celsius.

01:16 We need to find the pressure that this resulting gas is exerting in the flask okay so if we need to find the pressure of a gas the best way to do that is by using the ideal gas expression the product of pressure and volume equals the amount of gas in most times the ideal gas constant times the temperature in kelvin's so we need to find the pressure we have the volume, which is the volume of the container.

02:09 We don't have the amount of gas that is going to be collected.

02:16 R is a constant.

02:17 We find it, and we have the temperature here.

02:20 So we don't have p, we don't have n.

02:24 But there is a way we can find end because we know, or we have the information, that 2 .2 grams of 1 .4.

02:34 Idon is going to react with excess of hydrochloric acid.

02:39 Therefore, the gas, the mass of gas that is going to be obtained will depend on the amount of item that reacted and 2 .2 grams of iron completely reacted.

02:51 Therefore, we need to find the mass of item out of a stoichiometric relationship between iron and hydrogen gas.

03:02 This equation is balanced.

03:04 Therefore, we know now that one mole of iron will produce one mole of hydrogen gas.

03:15 And this is the mole ratio that we're going to establish between iron and hydrogen gas.

03:23 We have one mole of iron to one mole of hydrogen gas.

03:33 We need to convert this small relationship, this mole ratio, into a mass ratio because the information is given in mass, although we need to find n.

03:44 So we can also convert these 2 .2 grams into moles and we're gonna get directly the moles of hydrogen.

03:53 And that's the way i prefer.

03:55 So to convert these 2 .2 grams of iron into moles, all we have to do is divide by the atomic weight of iron, which is 55 .85 grams per mole.

04:13 Grams will cancel and we are left with moles in the denominator of a denominator, therefore it's going to be an numerator.

04:23 This is 2 .2 divided by 55 .85 and we get 0 .3939...

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