Question

Compare the mass of \(\mathrm{H}_{2}\) expected from the reaction of steam \(\left(\mathrm{H}_{2} \mathrm{O}\right)\) per mole of methane, petroleum, and coal. (Assume complete reaction in each case. Use \(\mathrm{CH}_{2}\) and \(\mathrm{CH}\) as representative formulas for petroleum and coal, respectively.

Short answer

Methane: 8 g, Petroleum: 4 g, Coal: 2 g of hydrogen per mole.

Step-by-step solution

- Write balanced chemical equations

First, write the balanced chemical equations for the reactions of methane, petroleum, and coal with steam. \[ \begin{align*} \text{Methane:} \quad & \text{CH}_4 + 2\text{H}_2\text{O} \rightarrow \text{CO}_2 + 4\text{H}_2 \ \text{Petroleum (CH}_2\text{):} \quad & \text{CH}_2 + \text{H}_2\text{O} \rightarrow \text{CO} + 2\text{H}_2 \ \text{Coal (CH):} \quad & \text{CH} + \text{H}_2\text{O} \rightarrow \text{CO} + \text{H}_2 \end{align*}\]

- Calculate moles of hydrogen produced

For each reaction, determine the number of moles of hydrogen gas that are produced per mole of reactant. \(\text{Methane: 4 moles of H}_2\), \(\text{Petroleum: 2 moles of H}_2\), and \(\text{Coal: 1 mole of H}_2\).

- Determine the molar mass of hydrogen gas

The molar mass of hydrogen gas \(\text{H}_2\) is \(2 \text{ g/mol}.\)

- Calculate mass of hydrogen produced

Use the number of moles of hydrogen gas from Step 2 and the molar mass from Step 3 to find the mass of hydrogen produced from each reactant. \[\begin{align*} \text{Methane:} \quad & 4 \text{ moles } \times 2 \text{ g/mol} = 8 \text{ g} \ \text{Petroleum:} \quad & 2 \text{ moles } \times 2 \text{ g/mol} = 4 \text{ g} \ \text{Coal:} \quad & 1 \text{ mole } \times 2 \text{ g/mol} = 2 \text{ g} \end{align*}\]

Key concepts

Chemical Reactions

Chemical reactions involve the transformation of one or more substances into new substances. These transformations occur when chemical bonds are broken and new bonds are formed. In the context of steam reforming for hydrogen production, different hydrocarbons react with steam. For instance, methane (CH\(_4\)), an abundant natural gas, can undergo a chemical reaction with steam to produce carbon dioxide and hydrogen gas. Other hydrocarbons like petroleum and coal also participate in similar reactions, though they result in different products and yields of hydrogen. The principle behind these reactions is to maximize hydrogen production by breaking the chemical bonds in hydrocarbons.

Stoichiometry

Stoichiometry is a core concept in chemistry used to calculate the amounts of reactants and products in a chemical reaction. It is based on the conservation of mass and energy, ensuring that the mass of reactants equals the mass of the products. With steam reforming, stoichiometry helps us determine the number of moles of hydrogen produced from a given quantity of hydrocarbon. Using the reaction's balanced chemical equations, we can see the stoichiometric coefficients, such as in methane reforming, where one mole of methane reacts with two moles of steam to produce four moles of hydrogen. Stoichiometry allows us to predict the output of hydrogen accurately, which is crucial for industrial applications.

Molar Mass

The concept of molar mass is essential in calculating the masses of substances involved in chemical reactions. Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For hydrogen gas (H\(_2\)), the molar mass is 2 g/mol. This value is derived by summing the atomic masses found on the periodic table. Knowing the molar masses of the reactants and products allows us to convert between moles and grams, facilitating the practical applications of stoichiometry. For example, understanding that one mole of hydrogen gas weighs 2 grams helps us quantitatively assess the yield of hydrogen from steam reforming.

Hydrogen Gas

Hydrogen gas, often seen as the fuel of the future, is a clean energy carrier with potential uses in fuel cells, industrial processes, and as a feedstock for various chemical productions. Produced extensively via steam reforming, hydrogen gas is noted for its high energy content per unit of weight. However, it must be carefully stored and handled due to its high flammability. The chemical formula for hydrogen gas is H\(_2\), indicating that it consists of two hydrogen atoms. Its production through steam reforming of hydrocarbons like methane, petroleum, and coal means that hydrogen can be sourced from a variety of feedstocks, aiding in the diversity and flexibility of hydrogen production.

Chemical Equations

Chemical equations are symbolic representations of chemical reactions, showing the reactants and the products, as well as their proportions. In steam reforming, balanced chemical equations are crucial for determining the amount of product generated from given reactants. The equations show the species involved, such as methane (CH\(_4\)), hydrogen (H\(_2\)), carbon monoxide (CO), and carbon dioxide (CO\(_2\)). Balancing these equations ensures that the law of conservation of mass is obeyed, with atoms being neither created nor destroyed in a reaction. This balance is crucial for accurately computing stoichiometry and optimizing processes like hydrogen production.