Question

Write the balanced chemical equation between Zn metal and HCl(aq). The other product is \(\mathrm{ZnCl}_{2}\)

Short answer

\( \text{Zn(s)} + 2\text{HCl(aq)} \rightarrow \text{ZnCl}_2(\text{aq}) + \text{H}_2(\text{g}) \)

Step-by-step solution

Identify Reactants and Products

The equation involves zinc metal, represented as \( \text{Zn(s)} \), and hydrochloric acid in aqueous form, represented as \( \text{HCl(aq)} \). The products are \( \text{ZnCl}_2 \), zinc chloride, and \( \text{H}_2 \), hydrogen gas.

Write the Unbalanced Equation

List the reactants and products: \( \text{Zn(s)} + \text{HCl(aq)} \rightarrow \text{ZnCl}_2(\text{aq}) + \text{H}_2(\text{g}) \). This is the skeleton equation showing all substances involved.

Balance Zn and Cl Atoms

Start with the balancing of \( \text{Zn} \) and \( \text{Cl} \) atoms. There is 1 zinc atom on both sides, so it's balanced. For chlorine, there are 2 chlorines in \( \text{ZnCl}_2 \), so place a coefficient of 2 before \( \text{HCl} \) to balance the chlorine: \( \text{Zn(s)} + 2\text{HCl(aq)} \rightarrow \text{ZnCl}_2(\text{aq}) + \text{H}_2(\text{g}) \).

Balance Hydrogen Atoms

Now, balance the hydrogen atoms. There are 2 hydrogen atoms in \( 2\text{HCl} \), which matches the 2 hydrogen atoms in \( \text{H}_2 \). Therefore, hydrogen is already balanced.

Verify the Overall Balance

Check to ensure that the number of each type of atom is equal on both sides of the equation. There is 1 zinc, 2 chlorine, and 2 hydrogen atoms on both sides of the equation making it balanced: \( \text{Zn(s)} + 2\text{HCl(aq)} \rightarrow \text{ZnCl}_2(\text{aq}) + \text{H}_2(\text{g}) \).

Key concepts

Stoichiometry

Stoichiometry is a fundamental aspect of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows chemists to predict how much of each substance is needed or produced in a given reaction.

When balancing chemical equations, stoichiometry ensures that the conservation of mass is maintained, meaning the number of atoms for each element is the same on both sides of the equation. For example, when balancing the reaction between zinc and hydrochloric acid, stoichiometry is used to ensure that the atoms of zinc, chlorine, and hydrogen are equally distributed among the reactants and products.

Here’s how stoichiometry works in this context:

• Determine the moles of each substance involved.
• Use the mole ratio to relate the quantities of reactants and products.
• Apply the balanced equation to calculate the masses or volumes of substances required or produced.

By understanding stoichiometry, students can solve complex chemical equations and appreciate the intricate balance present in chemical reactions.

Chemical Reactions

Chemical reactions are processes where substances, known as reactants, are transformed into different substances, called products. This transformation involves the reorganization of atoms and molecules through breaking and forming chemical bonds.

The reaction between zinc and hydrochloric acid is a classic example. Here, zinc displaces hydrogen from hydrochloric acid, resulting in the formation of zinc chloride and the release of hydrogen gas.

Key characteristics of chemical reactions include:

• Formation of new substances.
• Change in energy (exothermic or endothermic).
• Observable changes such as gas production, color change, or temperature variation.

By writing balanced chemical equations, we represent these reactions concisely and show the changes in atom arrangement explicitly. Balanced equations are essential for predicting the outcome of reactions under different conditions.

Zinc and Hydrochloric Acid Reaction

The reaction between zinc and hydrochloric acid is an example of a single-displacement reaction, where an element replaces another in a compound. In this specific reaction, zinc replaces the hydrogen in hydrochloric acid, forming zinc chloride soluble in water and releasing hydrogen gas.

The balanced chemical equation for this reaction is:
\[ ext{Zn(s)} + 2 ext{HCl(aq)} ightarrow ext{ZnCl}_2( ext{aq)} + ext{H}_2( ext{g)} \]

This equation shows that one mole of zinc reacts with two moles of hydrochloric acid to produce one mole of zinc chloride and one mole of hydrogen gas.

Important points to note about this reaction:

• It is a redox reaction, where zinc is oxidized, and hydrogen ions are reduced.
• The reaction evolves hydrogen gas, observable as bubbling in the solution.
• Careful measurements using stoichiometry can predict the product yield based on the amount of zinc and hydrochloric acid used.

Understanding such reactions not only provides insights into basic chemical principles but is also foundational for many industrial applications where metal processing and gas production are involved.