Question

Write the formula for each of the following compounds: a. ammonium hydrogen phosphate b. mercury(1) sulfide c. silicon dioxide d. sodium sulfite e. aluminum hydrogen sulfate f. nitrogen trichloride g. hydrobromic acid h. bromous acid i. perbromic acid j. potassium hydrogen sulfide k. calcium iodide I, cesium perchlorate

Short answer

a. \((NH_4)_2HPO_4\) b. \(Hg_2S\) c. \(SiO_2\) d. \(Na_2SO_3\) e. \(Al_2(HSO_4)_3\) f. \(NCl_3\) g. \(HBr\) h. \(HBrO_2\) i. \(HBrO_4\) j. \(KHS\) k. \(CaI_2\) l. \(CsClO_4\)

Step-by-step solution

a. ammonium hydrogen phosphate

Write the formula using the ions ammonium (NH₄⁺), hydrogen (H⁺), and phosphate (PO₄³⁻). The compound contains one phosphate ion, two ammonium ions, and one hydrogen ion to balance the charges, so the formula is (NH₄)₂HPO₄.

b. mercury(1) sulfide

Write the formula with mercury(I) ion (Hg₂²⁺) and sulfide ion (S²⁻). In this case, there is one mercury(I) ion and one sulfide ion, giving the formula Hg₂S.

c. silicon dioxide

Create a formula using silicon (Si) ions and oxygen ions (O²⁻), remembering that silicon typically has a charge of +4. Since two oxygen ions with a charge of -2 balance the charge of silicon, the formula is SiO₂.

d. sodium sulfite

Write the formula using sodium ions (Na⁺) and sulfite ions (SO₃²⁻). The compound contains one sulfite ion and two sodium ions to balance the charges, resulting in the formula Na₂SO₃.

e. aluminum hydrogen sulfate

Make a formula considering aluminum ions (Al³⁺), hydrogen ions (H⁺), and sulfate ions (SO₄²⁻). The compound must have two aluminum ions, one hydrogen ion, and three sulfate ions to achieve a neutral charge, leading to the formula Al₂(HSO₄)₃.

f. nitrogen trichloride

Combine nitrogen (N) ions (with a typical charge of -3) with chlorine (Cl) ions (with a charge of -1) to form a neutral compound. The formula is NCl₃ due to the 1:3 ratio of nitrogen to chlorine atoms, required to balance the charge.

g. hydrobromic acid

Write the formula using hydrogen ions (H⁺) and bromide ions (Br⁻). Hydrobromic acid is a binary acid, so the formula directly reflects the ions involved: HBr.

h. bromous acid

Use hydrogen ions (H⁺) and bromite ions (BrO₂⁻) to form the formula. Bromous acid is an oxyacid with the formula HBrO₂.

i. perbromic acid

Combine hydrogen ions (H⁺) with perbromate ions (BrO₄⁻) to form the formula. The formula for perbromic acid is HBrO₄.

j. potassium hydrogen sulfide

Create a formula using potassium ions (K⁺), hydrogen ions (H⁺), and sulfide ions (S²⁻). For a neutral compound, combine one potassium ion, one hydrogen ion, and one sulfide ion, resulting in the formula KHS.

k. calcium iodide

Write the formula using calcium ions (Ca²⁺) and iodide ions (I⁻). The compound consists of one calcium ion and two iodide ions to balance the charges, yielding the formula CaI₂.

I. cesium perchlorate

Formulate the compound using cesium ions (Cs⁺) and perchlorate ions (ClO₄⁻). The neutral formula consists of one cesium ion and one perchlorate ion, giving the formula CsClO₄.

Key concepts

Ionic Compounds

Ionic compounds are formed through the electrostatic attraction between positively charged ions (cations) and negatively charged ions (anions). These opposites attract, creating a stable compound. When writing the chemical formula for an ionic compound, it's key to ensure the total positive charge equals the total negative charge, leading to a neutral compound. For example, when combining sodium ( Na⁺ ) with sulfite ( SO₃^{2-} ), you need two sodium ions to balance with one sulfite ion, resulting in the formula Na₂SO₃ . This balance of charges is the cornerstone of writing ionic formulas. It's not only about the elements involved but how their charges interact.

Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms covalently bonded together, carrying an overall charge. Understanding these ions is crucial for the chemistry of compounds. A common example is the ammonium ion ( NH₄^+ ) and the sulfate ion ( SO₄^{2-} ). Polyatomic ions act as a single entity when forming compounds. For instance, ammonium hydrogen phosphate involves ammonium ( NH₄^+ ), hydrogen ( H^+ ), and phosphate ( PO₄^{3-} ). Combining these to form a neutral compound gives (NH₄)₂HPO₄ . Recognizing and remembering the formulas of common polyatomic ions is a useful skill in chemistry.

Acid Nomenclature

Acid nomenclature involves naming compounds that release hydrogen ions, H^+ , in solution. Different naming laws apply to binary acids, like hydrobromic acid ( HBr ), and oxyacids, which are acids containing oxygen. In oxyacids, the suffix changes depending on the central element's oxidation state. For example, HBrO₂ is named bromous acid, indicating an intermediate level of oxygen, while HBrO₄ is perbromic acid, showing a higher oxidation state. Mastery of acid nomenclature requires practice with identifying the type and charge of the acid in question.

Neutral Compound Formation

Neutral compound formation is the balancing act of creating compounds that have no net charge. Each compound's positive and negative components must cancel each other out. Take, for instance, the formation of aluminum hydrogen sulfate, Al₂(HSO₄)₃ , where you have aluminum ( Al^{3+} ) ions and hydrogen sulfate ( HSO₄^{-} ) ions. Achieving neutrality involves ensuring that the total positive charges match the total negative charges: with two aluminum ions (3+ each) and three hydrogen sulfate ions (-1 each), the compound balances to zero. This process is vital for writing correct chemical formulas.