Problem 38 - General Chemistry

Question

Some iron wire weighing \(5.6 \mathrm{~g}\) is placed in a beaker and covered with \(15.0 \mathrm{~g}\) of dilute hydrochloric acid. The acid reacts with the metal and gives off hydrogen gas, which escapes into the surrounding air. After reaction, the contents of the beaker weigh \(20.4 \mathrm{~g} .\) What is the mass of hydrogen gas produced by the reaction?

Step-by-Step Solution

Answer

The mass of hydrogen gas produced is 0.2 g.

Step 1: Understanding Mass Conservation

First, recognize that the law of conservation of mass states that mass cannot be created or destroyed in a closed system through chemical reactions. In this problem, the hydrochloric acid reacts with the iron to produce hydrogen gas, which escapes, changing the mass you measure.

Step 2: Calculating Initial Mass in Beaker

Calculate the total initial mass in the beaker before the reaction occurs. This is the sum of the mass of the iron wire and the dilute hydrochloric acid:\[m_{ ext{initial}} = 5.6 \, ext{g (iron)} + 15.0 \, ext{g (acid)} = 20.6 \, ext{g}\]

Step 3: Determine Mass After Reaction

Identify the mass of the beaker and its contents after the reaction:\[m_{ ext{after}} = 20.4 \, ext{g}\]

Step 4: Finding Mass of Escaped Hydrogen Gas

Calculate the mass of the hydrogen gas that escaped by finding the difference between the initial and final masses:\[m_{ ext{hydrogen}} = m_{ ext{initial}} - m_{ ext{after}} = 20.6 \, ext{g} - 20.4 \, ext{g} = 0.2 \, ext{g}\]

Step 5: Final Result

Thus, the mass of hydrogen gas produced and escaped during the reaction is: 0.2 g

Key Concepts

Chemical Reaction

A chemical reaction is a process where substances, known as reactants, undergo a transformation to form new substances, referred to as products. In this particular exercise, the chemical reaction taking place involves iron wire and hydrochloric acid reacting together to produce hydrogen gas and other compounds. During such reactions, chemical bonds are broken, and new ones are formed.

• The initial substances are iron wire and hydrochloric acid.
• The reaction results in the formation of new products, including hydrogen gas.
• Chemical reactions often involve energy changes, either releasing or absorbing heat.

Understanding chemical reactions involves recognizing the reactants and products and calculating the changes in mass or energy that occur as a result of the reaction.

Hydrochloric Acid

Hydrochloric acid is a strong, corrosive acid commonly used in laboratory and industrial settings. It consists of hydrogen and chlorine ions when dissolved in water. In this exercise, hydrochloric acid reacts with iron, facilitating the production of hydrogen gas.

• It's important to handle hydrochloric acid with care due to its corrosive nature.
• The reaction with iron helps demonstrate how acids can liberate hydrogen gas from metals.
• The acid itself takes part in dissolving the metal to form iron chloride in addition to releasing hydrogen gas.

This process underscores the reactive nature of acids, especially with metals, which is a fundamental concept in chemistry.

Iron Wire

Iron wire serves as one of the primary reactants in this chemical reaction. It's a form of elemental iron, often used in experiments due to its reactivity with acids. When you expose iron to hydrochloric acid, a reaction ensues, resulting in the formation of hydrogen gas and iron chloride.

• Iron is a metal known for its durability and magnetic properties.
• Its reactivity with acids like hydrochloric acid makes it ideal for demonstrations of chemical reactions.
• In this exercise, the iron wire reacts, reducing the iron into iron chloride, and thereby helping produce hydrogen gas.

The role of iron in this reaction exemplifies how metals react with acids to generate gases as by-products.

Hydrogen Gas Production

Hydrogen gas is produced as a result of a chemical reaction between iron wire and hydrochloric acid. In this scenario, it's the escaping gas measured to understand the mass change after the reaction takes place.

• Hydrogen gas is colorless, odorless, and highly flammable.
• The reaction is a practical example of an acid-metal reaction, which releases hydrogen gas.
• The mass of the produced hydrogen was calculated to be 0.2 g, based on the conservation of mass principles.

Producing hydrogen gas in this way highlights both the properties of acids and the practical uses of chemical reactions in producing gaseous products.