Question

What elements are present in each compound? (a) potassium iodide \(\mathrm{KI}\) (b) sodium carbonate \(\mathrm{Na}_{2} \mathrm{CO}_{3}\) (c) aluminum oxide \(\mathrm{Al}_{2} \mathrm{O}_{3}\) (d) calcium bromide \(\mathrm{CaBr}_{2}\) (e) acetic acid \(\mathrm{HC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\)

Short answer

KI: K, I; Na2CO3: Na, C, O; Al2O3: Al, O; CaBr2: Ca, Br; HC2H3O2: H, C, O

Step-by-step solution

Identify Elements in Potassium Iodide (KI)

Potassium iodide \(\text{KI}\) consists of the elements potassium (K) and iodine (I).

Identify Elements in Sodium Carbonate (Na2CO3)

Sodium carbonate \(\text{Na}_{2} \text{CO}_{3}\) consists of the elements sodium (Na), carbon (C), and oxygen (O).

Identify Elements in Aluminum Oxide (Al2O3)

Aluminum oxide \(\text{Al}_{2} \text{O}_{3}\) consists of the elements aluminum (Al) and oxygen (O).

Identify Elements in Calcium Bromide (CaBr2)

Calcium bromide \(\text{CaBr}_{2}\) consists of the elements calcium (Ca) and bromine (Br).

Identify Elements in Acetic Acid (HC2H3O2)

Acetic acid \(\text{HC}_{2} \text{H}_{3} \text{O}_{2}\) consists of the elements hydrogen (H), carbon (C), and oxygen (O).

Key concepts

Chemical Compounds

Chemical compounds are substances formed by two or more elements bonded together in fixed proportions. Each compound has unique properties that are different from the elements it contains. For example, water \(\text{H}_2\text{O}\) is made up of hydrogen and oxygen, but its properties are quite different from those of its constituent elements. Remember, compounds can have both physical (e.g., melting point, boiling point) and chemical (e.g., reactivity) properties.

This exercise explores identifying elements in given compounds. Understanding chemical compounds is essential in fields ranging from biochemistry to materials science.

Element Identification

Identifying elements in a compound involves deciphering its chemical formula, which provides a shorthand description of the types and quantities of elements present. For instance, in potassium iodide (\(\text{KI}\)), 'K' stands for potassium, and 'I' stands for iodine.

Each letter or group of letters represents an element's symbol from the periodic table, and subscripts (numbers written to the lower right of the element symbol) indicate how many atoms of each element are in the compound. If there is no subscript, it implies one atom.

By breaking down chemical formulas, you can clearly see which elements are linked in the compound and in what proportions.

Inorganic Chemistry

Inorganic chemistry deals with compounds not primarily made of carbon-hydrogen bonds. It includes a vast array of substances such as minerals, metals, and salts. The compounds in this exercise, like sodium carbonate (\(\text{Na}_2 \text{CO}_3\)) and aluminum oxide (\(\text{Al}_2 \text{O}_3\)), fall under inorganic chemistry.

Understanding inorganic compounds is crucial for fields such as geology, metallurgy, and industrial chemistry. These compounds often have significant roles in various industrial processes, forming the backbone of various materials like ceramics, glass, and metals.

Organic Chemistry

Organic chemistry focuses on carbon-containing compounds, especially those with carbon-hydrogen bonds. These include a vast variety of substances from fuels to polymers to proteins. In our exercise, acetic acid (\(\text{HC}_2 \text{H}_3 \text{O}_2\)) is an organic compound.

Organic chemistry is foundational to the study of life sciences since it explains the structure, properties, and reactions of compounds that form the basis of living organisms. For instance, acetic acid is a key component of vinegar, commonly used in food preservation and cooking. Understanding organic compounds is also critical for pharmaceuticals, petrochemicals, and materials science.

Chemical Formulas

Chemical formulas are a concise way of expressing information about the atoms in a chemical compound. They show the elements in the compound and their relative proportions. For example, calcium bromide (\(\text{CaBr}_2\)) tells us it contains calcium (Ca) and bromine (Br), with two bromine atoms for each calcium atom.

Mastery of reading and writing chemical formulas is essential for anyone studying chemistry. It provides a straightforward method to convey complex information and allows chemists to predict the properties and behaviors of substances.

In this exercise, recognizing these formulas is the key to identifying the elements present in each compound.