Question

Aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide. (a) Write the balanced chemical equation for this reaction. (b) How many grams of aluminum hydroxide are obtained from \(14.2 \mathrm{~g}\) of aluminum sulfide?

Short answer

The balanced chemical equation is \(Al_2S_3 + 6H_2O \rightarrow 2Al(OH)_3 + 3H_2S\). From 14.2 g of aluminum sulfide, approximately 14.76 g of aluminum hydroxide are obtained.

Step-by-step solution

Write the balanced chemical equation

For this reaction, we recall the compounds involved: - Aluminum sulfide (\(Al_2S_3\)) - Water (\(H_2O\)) - Aluminum hydroxide (\(Al(OH)_3\)) - Hydrogen sulfide (\(H_2S\)) Now, we combine them to create the chemical equation and balance it: \(Al_2S_3 + 6H_2O \rightarrow 2Al(OH)_3 + 3H_2S\)

Calculate moles of aluminum sulfide

Given the mass of aluminum sulfide (14.2 g), we can calculate its moles using its molar mass: Molar mass of \(Al_2S_3 = 2 \times 26.98 (Al) + 3 \times 32.07 (S) = 150.16 \mathrm{~g/mol}\) Using the equation, Moles of \(Al_2S_3 = \frac{Mass}{Molar Mass}\) Moles of \(Al_2S_3 = \frac{14.2 \mathrm{~g}}{150.16 \mathrm{~g/mol}} \approx 0.0946 \mathrm{~mol}\)

Use stoichiometry to convert moles of aluminum sulfide to moles of aluminum hydroxide

Looking at the balanced chemical equation, we see that the stoichiometric ratio of aluminum sulfide to aluminum hydroxide is \(1:2\), meaning: 1 mole of aluminum sulfide produces 2 moles of aluminum hydroxide. Using this information, we can determine the moles of aluminum hydroxide produced from the given moles of aluminum sulfide: Moles of \(Al(OH)_3 = 2 \times 0.0946 \mathrm{~mol} = 0.1892 \mathrm{~mol}\)

Convert moles of aluminum hydroxide to grams

Now, we will convert the moles of aluminum hydroxide to grams using its molar mass: Molar mass of \(Al(OH)_3 = 26.98 (Al) + 3 \times (15.999 \times 1.008 + 15.999)\mathrm{~g/mol} = 78.00 \mathrm{~g/mol}\) To find the mass of aluminum hydroxide produced, we use the equation: Mass of \(Al(OH)_3 = Moles \times Molar Mass\) Mass of \(Al(OH)_3 = 0.1892 \mathrm{~mol} \times 78.00 \mathrm{~g/mol} \approx 14.76 \mathrm{~g}\) So, approximately 14.76 grams of aluminum hydroxide are obtained from 14.2 grams of aluminum sulfide.

Key concepts

Stoichiometry

Stoichiometry is a fundamental concept in chemistry that involves the calculation of reactants and products in chemical reactions. It's like a recipe, ensuring you have the right amounts to create a chemical product without leftovers. To understand stoichiometry, imagine baking cookies. You need specific amounts of flour, sugar, and butter to make them; too much or too little of any ingredient will lead to results that are less than ideal.

In the context of a chemical reaction, stoichiometry is based on the balanced chemical equation. This equation provides the proportions, known as stoichiometric coefficients, of each substance involved. For example, in the reaction between aluminum sulfide and water to produce aluminum hydroxide and hydrogen sulfide, the balanced equation is:

• 1 molecule of \( Al_2S_3 \) reacts with 6 molecules of \( H_2O \).
• This produces 2 molecules of \( Al(OH)_3 \) and 3 molecules of \( H_2S \).

Understanding stoichiometry helps you predict how much product you'll get from a given amount of reactant or how much reactant you need to produce a desired amount of product. Mastering it is essential for any chemistry-related field.

Molar Mass

Molar mass is the mass of one mole of a chemical substance. It's a crucial concept in chemistry as it allows us to convert between the mass of a substance and the amount in moles, which is essential for quantifying chemical reactions accurately.

To determine molar mass, you simply add up the atomic masses of each element in a compound according to its chemical formula. For example, the molar mass of aluminum sulfide \( (Al_2S_3) \) is calculated as follows:

• Aluminum \( (Al) \) has an atomic mass of approximately 26.98 g/mol.
• Sulfur \( (S) \) has an atomic mass of approximately 32.07 g/mol.
• For \( Al_2S_3 \), it's \((2 \times 26.98) + (3 \times 32.07) = 150.16 \text{ g/mol}.\)

Using molar mass, you can convert grams of a substance to moles or vice versa using the formula:
\[\text{Moles} = \frac{\text{Mass in grams}}{\text{Molar mass in g/mol}}\]

Knowing the molar mass is key for solving problems related to the mass and quantity of substances in chemical reactions.

Chemical Reactions

Chemical reactions are processes in which substances, known as reactants, transform into new substances, called products. These transformations involve the breaking and forming of chemical bonds, changing the identity and properties of the substances involved.

Take the reaction between aluminum sulfide and water, for example. Initially, you have aluminum sulfide and water as reactants. These then undergo a chemical reaction to form aluminum hydroxide and hydrogen sulfide as products.

• The process is represented by a balanced chemical equation: \( Al_2S_3 + 6H_2O \rightarrow 2Al(OH)_3 + 3H_2S \).
• This equation indicates not only the substances involved but also their stoichiometric relationships.

Chemical reactions are all around us, from the rusting of iron to the digestion of food. They can be classified in various ways—such as synthesis, decomposition, single replacement, or double replacement—depending on how the reactants and products interact.

Understanding chemical reactions is crucial, as they are fundamental to the study of chemistry and the explanation of many natural phenomena.