Question

Write the formula for each of the following compounds, and indicate the oxidation state of the halogen: (a) Bromic acid (b) Hypoiodous acid

Short answer

Bromic acid: \( HBrO_3 \), bromine: +5; Hypoiodous acid: \( HIO \), iodine: +1.

Step-by-step solution

Identify the Formula for Bromic Acid

Bromic acid is composed of bromine, oxygen, and hydrogen. Bromic acid has the formula \( HBrO_3 \), derived from its parent compound bromine trioxide \( BrO_3^- \). It consists of a bromate ion bonded to a hydrogen ion.

Determine the Oxidation State of Bromine in Bromic Acid

To find the oxidation state of bromine in \( HBrO_3 \), set up an equation using known oxidation states. Hydrogen has an oxidation state of +1, and oxygen has -2. The equation is: \( +1 + x + 3(-2) = 0 \) where \( x \) is the oxidation state of bromine. Solving, \( +1 + x - 6 = 0 \) gives \( x = +5 \). Therefore, bromine has an oxidation state of +5 in bromic acid.

Identify the Formula for Hypoiodous Acid

Hypoiodous acid consists of iodine, oxygen, and hydrogen. Its formula is \( HIO \), an acid derived from the hypoiodite ion \( IO^- \). This compound corresponds to the hypoiodite form of iodine.

Determine the Oxidation State of Iodine in Hypoiodous Acid

In \( HIO \), hydrogen has an oxidation state of +1, and oxygen is -2. The equation to find the iodine (\( x \)) oxidation state is: \( +1 + x + (-2) = 0 \). Solving, \( x - 1 = 0 \) results in \( x = +1 \). Thus, iodine's oxidation state in hypoiodous acid is +1.

Key concepts

Oxidation State

The oxidation state is a concept in chemistry that represents the degree of oxidation of an atom in a chemical compound. It helps to determine how electrons are distributed in that compound.
For example:

• In many compounds, elements like hydrogen usually exhibit an oxidation state of +1, and oxygen shows -2.
• The oxidation state can often be calculated using simple algebraic equations where the sum of all oxidation states in a neutral compound equals zero.
• Different elements may have different common oxidation states; depending on their position in the periodic table and the compounds they're part of.

Understanding oxidation states is crucial in predicting the chemical reactivity and properties of compounds. It can also help in balancing chemical equations and in comprehending redox reactions.

Bromic Acid

Bromic acid is a compound consisting of bromine, oxygen, and hydrogen, and it has the chemical formula \( HBrO_3 \).
Here are some key details:

• The acid is derived from the bromate ion, \( BrO_3^- \), which forms when bromine (a halogen) is in a highly oxidized state.
• In bromic acid, the oxidation state of bromine is +5, reflecting its high level of oxidation. This is found by balancing the sum of the known oxidation states: hydrogen is +1, oxygen is -2, and the total charge of the molecule sums to zero.
• Bromic acid is a strong oxidizing agent due to the high oxidation state of bromine. This means it can easily gain electrons in chemical reactions.

Bromic acid is less commonly encountered than some other acids in laboratory settings but demonstrates important reactivity rules of bromine and other halogens.

Hypoiodous Acid

Hypoiodous acid features the elements iodine, oxygen, and hydrogen, with the formula \( HIO \).
Important points to know include:

• The acid is derived from the hypoiodite ion \( IO^- \), indicating a lower oxidation state of iodine compared to other iodine acids such as iodic or periodic acid.
• In hypoiodous acid, iodine exhibits an oxidation state of +1. This is determined by setting the known oxidation states, where hydrogen is +1 and oxygen is -2, and solving for iodine.
• This compound is relatively unstable and tends to decompose, making it less common in storage but significant in certain reactions where a mild oxidizing agent is needed.

Hypoiodous acid showcases the varied oxidation states that halogens can possess, especially iodine, making it an interesting study in halogen chemistry.