Question

Write a formula for the compound that forms from potassium and (a) acetate (b) chromate (c) phosphate (d) cyanide

Short answer

The formulas for the compounds that form from potassium and (a) acetate, (b) chromate, (c) phosphate, (d) cyanide are (a) KC2H3O2, (b) K2CrO4, (c) K3PO4, (d) KCN respectively.

Step-by-step solution

Identify the Ions

Potassium is represented by the symbol K with a +1 charge (K+). Acetate is represented by the formula C2H3O2 with a -1 charge (C2H3O2-). Chromate is represented by the formula CrO4 with a -2 charge (CrO4^2-). Phosphate is represented by the formula PO4 with a -3 charge (PO4^3-). Cyanide is represented by the formula CN with a -1 charge (CN-).

Write the Formula for Potassium Acetate

Since potassium has a +1 charge and acetate has a -1 charge, they combine in a 1:1 ratio to form potassium acetate, which is K+ (C2H3O2)-, yielding the formula KC2H3O2.

Write the Formula for Potassium Chromate

Potassium has a +1 charge and chromate has a -2 charge, so two potassium ions are needed for each chromate ion to balance the charge, forming K2CrO4.

Write the Formula for Potassium Phosphate

Potassium has a +1 charge and phosphate has a -3 charge, so three potassium ions are needed for each phosphate ion to balance the charge, forming K3PO4.

Write the Formula for Potassium Cyanide

Since potassium has a +1 charge and cyanide has a -1 charge, they combine in a 1:1 ratio to form potassium cyanide, which is K+ (CN)-, yielding the formula KCN.

Key concepts

Ion Charge Balance

Understanding ion charge balance is fundamental when writing formulas for ionic compounds. It's all about ensuring that the positive and negative charges in a compound cancel each other out, leading to a neutral overall charge. For example, when we look at potassium (K) with a +1 charge and acetate (C2H3O2) with a -1 charge, they naturally balance each other in a 1:1 ratio. Thus, one potassium ion pairs with one acetate ion to form potassium acetate (KC2H3O2), with no excess charge.

When it gets a bit tricky is with ions that have different charges, such as a single potassium ion (+1) and a chromate ion (CrO4) with a -2 charge. To achieve neutrality, we require two potassium ions for every one chromate ion, resulting in the formula K2CrO4. The concept is like a seesaw where both sides must be equally weighted to be balanced, conceptually visualizing how charges need to align to create stability within the chemical compound.

Ionic Compounds

Ionic compounds are substances formed by the chemical bonding of cations (positively charged ions) and anions (negatively charged ions) through ionic bonds. The essence of their formation is the transfer of electrons from a metal (which becomes a cation) to a non-metal (which becomes an anion).

Take potassium phosphate, derived from the ions potassium (K+) and phosphate (PO4^3-). Due to their charges, a 3:1 ratio of potassium to phosphate ions is required to form the ionic compound K3PO4. The three potassium ions (each with a +1 charge) completely balance out the single phosphate ion (with a -3 charge), resulting in a neutral ionic compound. These ionic compounds are stable because the total charge must always come out to zero - nature's way of seeking balance.

Chemical Nomenclature

Chemical nomenclature is a systematic way of naming chemical substances. This naming system ensures that each compound has a unique and universally recognized name, which reflects its composition and structure. In our exercise, potassium cyanide is named by identifying the cation, potassium (K+), followed by the anion, cyanide (CN-). By understanding the ions involved and their charges, we deduced the formula KCN.

Using standardized nomenclature guidelines helps chemists communicate efficiently and accurately. For instance, when writing formulas, it’s important to use subscripts to indicate the number of ions in an ionic compound. For K2CrO4, the '2' subscript after K signifies that two potassium ions are present. These rules maintained across the field enable students and scientists to make sense of chemical formulas and compositions without ambiguity.