Question

Magnesium metal reacts with acid to produce hydrogen gas. The gas displaces water from a graduated cylinder, and the water level decreases from \(95.0 \mathrm{~mL}\) to \(32.5 \mathrm{~mL}\). What is the volume of gas produced by the reaction?

Short answer

The volume of gas produced is 62.5 mL.

Step-by-step solution

Understand the Scenario

The question describes a reaction where magnesium metal reacts with an acid, producing hydrogen gas. This gas displaces water in a graduated cylinder, causing the water level to decrease.

Determine Initial Water Level

Identify the initial water level in the graduated cylinder, which is given as 95.0 mL.

Determine Final Water Level

Identify the final water level in the graduated cylinder after the reaction, which is given as 32.5 mL.

Calculate Change in Water Level

Subtract the final water level from the initial water level to find the change in water level, which represents the volume of gas produced:\[ \text{Volume of gas} = 95.0 \, \text{mL} - 32.5 \, \text{mL} \]

Compute Volume of Gas Produced

Perform the subtraction:\[ 95.0 \, \text{mL} - 32.5 \, \text{mL} = 62.5 \, \text{mL} \]So, the volume of gas produced by the reaction is 62.5 mL.

Key concepts

Gas Volume Calculation

When dealing with chemical reactions that produce gas, such as the reaction between magnesium and acid, measuring the gas volume is crucial. In the given exercise, we read about how hydrogen gas displaces water in a graduated cylinder. To find the volume of gas produced, we only need to measure how much the water level in the cylinder changes.
The process goes like this:

• Step 1: Record the initial water level in the graduated cylinder (95.0 mL).
• Step 2: After the reaction completes, measure the final water level (32.5 mL).
• Step 3: Calculate the volume of the gas by subtracting the final water level from the initial water level.

For example, for our exercise, the difference between the initial and final levels of the water is 62.5 mL, indicating the volume of hydrogen gas produced (since 95.0 mL - 32.5 mL = 62.5 mL).
This simple calculation can be applied to various experiments when gases are involved and they displace a liquid under standard conditions.

Stoichiometry

Stoichiometry involves the detailed calculation of reactants and products in a chemical reaction. In our exercise, magnesium reacts with an acid to produce hydrogen gas. To fully understand stoichiometry, we need to look at the balanced chemical equation.Let's consider the reaction:\[ \text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2 \]From the equation, we see that one mole of magnesium reacts with two moles of hydrochloric acid to produce one mole of hydrogen gas and one mole of magnesium chloride. This represents a 1:2:1:1 ratio; this is stoichiometry in action.
To determine how much of each substance is involved or produced, you can use the stoichiometric coefficients. These coefficients help ensure that atoms are conserved across the reaction equation. It allows you to make predictions about how much reactant is needed or how much product will be formed under ideal conditions.
For calculations involving gas volume in experiments, you might be applying the ideal gas law or assumptions about standard pressure and temperature, which further ties into using stoichiometric principles effectively in lab settings.

Experiments in Chemistry

Chemistry experiments, like the one described, help us see chemical reactions in action. They often provide measurable results, such as gas volume, that support learning concepts like reaction stoichiometry. In our setup:

• We have magnesium reacting with hydrochloric acid, serving as a terrific visual example of chemical reactivity and gas production.
• The change in water volume in a graduated cylinder shows how reactions can produce gases, which can be measured straightforwardly.

When conducting experiments:

• Safety is paramount. Always wear protective gear.
• Measurements should be as accurate as possible for reliable results.
• Precision instruments, like graduated cylinders, are common tools for these observations.

Experiments not only put theory into practice but also provide a better grasp of the underlying scientific principles. They are essential for understanding how abstract concepts in chemistry apply to real-world phenomena and are particularly useful for learning how to predict and analyze the behavior of chemical reactions.