Question

Without doing any calculations, arrange the elements in \(\mathrm{H}_{2} \mathrm{SO}_{4}\) in order of decreasing mass percent composition.

Short answer

The elements in \(\mathrm{H}_{2}SO_{4}\) arranged in order of decreasing mass percent composition are Oxygen (O), Sulfur (S), Hydrogen (H).

Step-by-step solution

Identify the Molar Masses

Find the molar mass of each element in the compound \(\mathrm{H}_{2}SO_{4}\) using the periodic table. Sulfur (S) typically has the highest molar mass, followed by Oxygen (O), and the least being Hydrogen (H).

Determine the Total Mass of Each Element

For a qualitative assessment, determine the total mass of each element by considering the number of atoms of each element in the molecule. \(\mathrm{H}_{2}\) has 2 atoms of Hydrogen, \(\mathrm{SO}_{4}\) has 1 atom of Sulfur and 4 atoms of Oxygen.

Arrange by Mass Percent

Arrange the elements in order of the mass percent without calculations by considering that the element with the highest molar mass and number of atoms will contribute more to the total mass of the compound. The element with fewer atoms or lower molar mass will contribute less.

Key concepts

Molar Mass

Understanding the concept of molar mass is crucial when studying chemistry and engaging in exercises such as determining mass percent composition. Molar mass, simply put, is the mass of one mole of a substance (usually in grams per mole). It reflects the weight of all atoms within a chemical compound's formula.

Molar mass is calculated by summing up the atomic masses of each element in a molecule, with consideration for how many atoms of each element are present. For instance, in water (H₂O), molar mass is the combined mass of 2 hydrogen atoms and 1 oxygen atom. The atomic masses are found on the periodic table, where hydrogen has an atomic mass of approximately 1 gram per mole and oxygen has an atomic mass of about 16 grams per mole.

The accurate determination of molar mass is a stepping stone to finding out how much of each element contributes to the total mass of a compound, which in turn is essential for stoichiometry and understanding chemical reactions.

Stoichiometry

Stoichiometry is the section of chemistry that pertains to the quantitative relationships that govern the reactants and products in chemical reactions. It is a foundational concept that relies on the law of conservation of mass and the stoichiometric coefficients provided in a balanced chemical equation.

In practical terms, stoichiometry is used to predict how much reactant is needed to produce a desired amount of product, or conversely, how much product can be made from a given amount of reactant. This involves using the molar mass of substances to convert between mass and moles and understand the ratios of substances involved. For example, the stoichiometric calculation in the case of combustion reactions would entail ensuring that oxygen is present in a sufficient quantity to react with a given amount of a hydrocarbon fuel.

When it comes to ordering elements by mass percent composition, stoichiometry provides the framework for understanding the relative contributions of each element within a compound, thereby simplifying complex chemical relationships into comprehensible numerical ratios.

Chemical Composition

Chemical composition refers to the identity and quantity of the elements that make up a chemical compound. It's essentially a breakdown of a substance into its constituent elements, specifying the exact number of atoms of each element present in the compound. The chemical composition is integral when considering properties like reactivity, toxicity, and molecular function.

Mass percent composition, in particular, expresses the mass of each element relative to the total mass of the compound, presented as a percentage. To establish the chemical composition in terms of mass percent, one must first understand the molar masses of the elements and the stoichiometry of the compound. For instance, water has two parts hydrogen and one part oxygen by volume; however, by mass, the composition is roughly 11% hydrogen and 89% oxygen due to the differences in molar mass.

Having a clear understanding of chemical composition is essential for students and professionals in various scientific fields. It enables the comparison of different substances and aids in the prediction of how compounds will interact with each other, which is crucial for applications ranging from pharmaceuticals to materials science.