Question

Hydrogen gas reacts with each of the halogen elements to form the hydrogen halides (HF, HCl, HBr, HI). Calculate the percent by mass of hydrogen in each of these compounds.

Short answer

The percent by mass of hydrogen in each hydrogen halide is as follows: - HF: 5% - HCl: 2.74% - HBr: 1.23% - HI: 0.78%

Step-by-step solution

Find the atomic masses of the elements

Obtain the atomic masses of the elements from the periodic table: - Hydrogen (H) has an atomic mass of 1 g/mol. - Fluorine (F) has an atomic mass of 19 g/mol. - Chlorine (Cl) has an atomic mass of 35.5 g/mol. - Bromine (Br) has an atomic mass of 80 g/mol. - Iodine (I) has an atomic mass of 127 g/mol.

Calculate the total mass of each hydrogen halide

Compute the total mass of each hydrogen halide using the atomic masses of the elements: - HF: \(1 + 19 = 20\) g/mol - HCl: \(1 + 35.5 = 36.5\) g/mol - HBr: \(1 + 80 = 81\) g/mol - HI: \(1 + 127 = 128\) g/mol

Calculate the percent by mass of hydrogen in each hydrogen halide

Compute the percent by mass of hydrogen by dividing the mass of hydrogen with the total mass of the compound, and multiplying by 100: - %H in HF: \(\frac{1}{20} \times 100 = 5% \) - %H in HCl: \(\frac{1}{36.5} \times 100 \approx 2.74% \) - %H in HBr: \(\frac{1}{81} \times 100 \approx 1.23% \) - %H in HI: \(\frac{1}{128} \times 100 \approx 0.78% \)

Final Results:

The percent by mass of hydrogen in each hydrogen halide is as follows: - HF: 5% - HCl: 2.74% - HBr: 1.23% - HI: 0.78%

Key concepts

Understanding Atomic Mass Calculation

To calculate the percent by mass of hydrogen in compounds, it's important to first understand atomic mass calculation. Atomic mass is the weight of an atom of a chemical element, usually expressed in unified atomic mass units (u). Each element on the periodic table has a specific atomic mass.

The atomic mass of an element represents the average mass of all its isotopes, taking their abundances into account. In calculations, we often use atomic masses measured in grams per mole (g/mol) to perform stoichiometric calculations in chemistry. For example, hydrogen has an atomic mass of approximately 1 g/mol.

When determining atomic mass for compounds, such as the hydrogen halides (HF, HCl, HBr, HI), it involves adding the atomic masses of the constituent atoms:

• HF consists of one hydrogen atom (1 g/mol) and one fluorine atom (19 g/mol), resulting in a total mass of 20 g/mol.
• Similarly, HCl is composed of hydrogen and chlorine (35.5 g/mol), totaling 36.5 g/mol.

Mastering atomic mass calculations is essential for determining percent mass and understanding the composition of chemical substances.

Exploring Hydrogen Halides

Hydrogen halides are a group of compounds formed when hydrogen bonds with halogens. The halogens are elements found in Group 17 of the periodic table and consist of fluorine, chlorine, bromine, and iodine.

These hydrogen halides (e.g., HF, HCl, HBr, HI) are crucial in chemistry due to their reactivity and variety of uses in chemical synthesis.

Each hydrogen halide is a gaseous compound at room temperature and has distinct properties based on the halogen present:

• HF, or hydrogen fluoride, is a weak acid in aqueous solutions and is known for etching glass.
• HCl, or hydrogen chloride, when dissolved in water becomes hydrochloric acid, a strong and commonly used acid in laboratories.

The bond between hydrogen and halogens involves hydrogen's single electron and the valence electrons of halogens, forming a covalent bond. Understanding hydrogen halides' formation and their properties is fundamental for analyzing their chemical behavior.

Chemical Reactions with Halogens

Halogens are highly reactive nonmetals due to their seven valence electrons, which means they are eager to gain another electron to achieve a stable octet configuration. This characteristic makes them highly reactive with hydrogen.

When halogens react with hydrogen, they form hydrogen halides, such as HF, HCl, HBr, and HI. These reactions are typically direct combination reactions, meaning they involve the direct combination of hydrogen gas and halogen gas under suitable conditions, often forming the hydrogen halides spontaneously.

For example, when chlorine gas (\[Cl_2\]) reacts with hydrogen gas (\[H_2\]), it forms hydrogen chloride (HCl): \[H_2 + Cl_2 \rightarrow 2HCl\]

• This reaction is highly exothermic, meaning it releases a significant amount of energy.
• Other halogens like bromine and iodine also readily react with hydrogen under suitable conditions in a similar manner.

Understanding these reactions is key to studying how halogens and hydrogen transform into useful compounds through chemical processes.