Question

A \(2.45-g\) sample of strontium completely reacts with oxygen to form \(2.89 \mathrm{~g}\) of strontium oxide. Use this data to calculate the mass percent compostaon of strontium in strontium coxide.

Short answer

The mass percent composition of strontium in strontium oxide is approximately 84.78%.

Step-by-step solution

Calculate the mass of oxygen that reacted with strontium

To determine the mass of oxygen that reacted, subtract the mass of the strontium from the mass of the strontium oxide formed. This will give you the mass of oxygen that has combined with the strontium during the reaction.

Calculate the mass percent of strontium in strontium oxide

The mass percent of strontium in strontium oxide is calculated by dividing the mass of strontium by the mass of strontium oxide and then multiplying by 100 to convert it to a percentage.

Key concepts

Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. This concept is pivotal because it allows chemists to predict the amounts of substances consumed and produced during a reaction. For students grappling with stoichiometry, the strontium and oxygen reaction serves as a practical example.

In the provided exercise, the stoichiometry of the reaction between strontium and oxygen involves calculating the amount of oxygen that reacts with a known mass of strontium to form strontium oxide. To fully understand stoichiometry, one must grasp the law of conservation of mass, which states that matter is neither created nor destroyed in a chemical reaction. Hence, the total mass of the reactants (strontium and oxygen) must equal the total mass of the products (strontium oxide) after the reaction.

Here's a simplified approach to solving stoichiometry problems: First, identify the reactants and products. Next, measure the mass of the reactants before the reaction and the mass of the products after the reaction. Applying this knowledge to the problem can help you determine the amount of each reactant that was used and the amount of each product that was formed.

Chemical Reaction

A chemical reaction involves the transformation of one or more substances into new substances with differing chemical properties. In the context of the given exercise, strontium reacts with oxygen in a chemical reaction to form strontium oxide. The reaction can be summarized in a chemical equation, which visually represents the process and helps identify the reactants and products.

To simplify, during chemical reactions, reactants (in this case, strontium and oxygen) interact to form products (strontium oxide). This particular type of reaction where a metal reacts with oxygen is called a synthesis reaction, one of the basic types of chemical reactions. Understanding the type of reaction helps in predicting the products and the ratios in which reactants combine.

For better comprehension, students should not only focus on the numerical aspects of the reaction but also on the conceptual understanding of what is happening during the reaction. Visualizing or sketching the reactants and products can aid in digesting the concept more profoundly. Moreover, balancing the chemical equation ensures that the law of conservation of mass is upheld, which is crucial for the stoichiometric calculations.

Empirical Formula

The empirical formula of a compound represents the simplest whole number ratio of elements in it. This formula does not necessarily represent the exact number of atoms in a single molecule of a compound, but it gives insight into the proportional relationship between its constituent elements. In the current exercise, although we're not asked to determine the empirical formula directly, the concept is closely related to the stoichiometric calculations and the mass percent composition.

To grasp the concept of empirical formulas, it is helpful to understand that they are derived from the mass composition of a compound. By knowing the mass of each element in a compound and their relative atomic masses, one can calculate the moles of each element. These ratios of moles can then be simplified to find the empirical formula. For instance, in the strontium oxide created in the exercise, if we knew the moles of strontium and oxygen, we could deduce the empirical formula.

Learning to calculate empirical formulas is a cornerstone in chemistry, as it leads to a deeper understanding of molecular composition and can be used to determine molecular formulas as well. Students are encouraged to practice deriving empirical formulas from percentage composition data to master this concept.