Problem 23 - Chemistry The Central Science

Question

Write a balanced equation for the preparation of \(\mathrm{H}_{2}\) using (a) \(\mathrm{Mg}\) and an acid, (b) carbon and steam, (c) methane and steam.

Step-by-Step Solution

Answer

(a) \(Mg + 2HCl \rightarrow MgCl_2 + H_2 \) (b) \(C + H_2O \rightarrow CO_2 + H_2 \) (c) \(CH_4 + H_2O \rightarrow CO + 3H_2 \)

Step 1: (a) Magnesium and Acid

First, we need to select an acid to react with magnesium. Hydrochloric acid (HCl) will be used in this case. The general word equation is: Magnesium + Hydrochloric Acid → Magnesium Chloride + Hydrogen gas Now, convert the word equation into a chemical equation: \( Mg + HCl \rightarrow MgCl_2 + H_2 \) We need to balance the equation by adjusting the coefficients: \( Mg + 2HCl \rightarrow MgCl_2 + H_2 \) The balanced equation for the reaction of magnesium with hydrochloric acid is: \(Mg + 2HCl \rightarrow MgCl_2 + H_2 \)

Step 2: (b) Carbon and Steam

The word equation for carbon and steam forming hydrogen gas and carbond dioxide is: Carbon + Steam → Carbon Dioxide + Hydrogen gas Now, convert the word equation into a chemical equation: \( C + H_2O \rightarrow CO_2 + H_2 \) The equation is already balanced, so the balanced equation for the reaction of carbon with steam is: \(C + H_2O \rightarrow CO_2 + H_2 \)

Step 3: (c) Methane and Steam

The word equation for methane and steam forming carbon monoxide and hydrogen gas is: Methane + Steam → Carbon Monoxide + Hydrogen gas Now, convert the word equation into a chemical equation: \( CH_4 + H_2O \rightarrow CO + H_2 \) We need to balance the equation by adjusting the coefficients: \( CH_4 + H_2O \rightarrow CO + 3H_2 \) The balanced equation for the reaction of methane with steam is: \(CH_4 + H_2O \rightarrow CO + 3H_2 \)

Key Concepts

Chemical Reaction

When we discuss chemical reactions, we're examining the process where substances, known as reactants, are transformed into different substances called products. It's like a culinary recipe, but instead of making a cake, we're creating new chemical compounds.

For instance, when magnesium reacts with hydrochloric acid, the magnesium replaces the hydrogen in the acid, which results in magnesium chloride and hydrogen gas. This switcheroo is called a single displacement reaction.

Understanding Reactants and Products

To ensure students grasp this concept, think of chemical reactions as social exchanges where elements 'swap partners'. Magnesium was 'single', met hydrochloric acid, a 'couple', and then partnered with chlorine, letting hydrogen 'single' float away as a gas.

Stoichiometry

Stoichiometry is essentially the 'accounting' of chemistry. It ensures that atoms are conserved in a reaction, following the law of conservation of mass. You could liken it to a seesaw — what goes up must come down, maintaining a balance.

To balance chemical equations, you adjust the coefficients, the numbers before the chemical formulas, until you have equal numbers of each type of atom on both sides of the equation. Think of it as making sure you have the same number of forks as knives at a dinner setting for each guest, so everyone can both cut and eat their food.

Making It Relatable

To help students visualize, use everyday examples, like ensuring you have an equal amount of shoes for each foot — unless you're a centipede, one shoe for each foot will always strike a balance!

Gas Evolution Reactions

Gas evolution reactions are a thrilling spectacle in chemistry where a gas is produced as a product of the reaction, much like a fizzy soda releasing carbon dioxide when opened.

These reactions are fun to watch and signify that new bonds are forming and old bonds are breaking. For instance, metal carbonates or bicarbonates react with acids to release carbon dioxide gas. Picture this as popping the cork off a champagne bottle, where the pressure built-up releases the gas and everyone cheers.

Recognizing the Bubbles

When students are working through these problems, encourage them to look for telltale signs of gas production, like bubbling or fizzing. It's the chemical equivalent of hearing the sizzle when you're cooking — it tells you something exciting is happening!