Question

You are given 1.00 gram of each of five substances. In which of the substances will there be the greatest number of potassium ions when dissolved in water? a. potassium chloride b. potassium chlorate c. potassium phosphate d. potassium nitrate e. potassium carbonate

Short answer

The compound with the greatest number of potassium ions when dissolved in water is e. potassium carbonate (K2CO3) with 0.01448 moles of potassium ions.

Step-by-step solution

Identify the number of potassium ions in each compound

Determine the number of potassium ions in one molecule of each compound. a. Potassium chloride (KCl) - 1 potassium ion b. Potassium chlorate (KClO3) - 1 potassium ion c. Potassium phosphate (K3PO4) - 3 potassium ions d. Potassium nitrate (KNO3) - 1 potassium ion e. Potassium carbonate (K2CO3) - 2 potassium ions

Calculate the molar mass of each compound

We will calculate the molar mass of each compound using the atomic masses of the elements. a. KCl: 39.10 (K) + 35.45 (Cl) = 74.55 g/mol b. KClO3: 39.10 (K) + 35.45 (Cl) + 3 x 16.00 (O) = 122.55 g/mol c. K3PO4: 3 x 39.10 (K) + 30.97 (P) + 4 x 16.00 (O) = 212.27 g/mol d. KNO3: 39.10 (K) + 14.01 (N) + 3 x 16.00 (O) = 101.10 g/mol e. K2CO3: 2 x 39.10 (K) + 12.01 (C) + 3 x 16.00 (O) = 138.21 g/mol

Calculate the moles of each compound and moles of potassium ions

Determine the moles of each compound when given 1.00 gram, and calculate the number of moles of potassium ions based on the number of potassium ions per molecule. a. KCl: (1.00 g) / (74.55 g/mol) = 0.01341 mol KCl Moles of K: 0.01341 mol b. KClO3: (1.00 g) / (122.55 g/mol) = 0.00816 mol KClO3 Moles of K: 0.00816 mol c. K3PO4: (1.00 g) / (212.27 g/mol) = 0.00471 mol K3PO4 Moles of K: 3 x 0.00471 mol = 0.01414 mol d. KNO3: (1.00 g) / (101.10 g/mol) = 0.00989 mol KNO3 Moles of K: 0.00989 mol e. K2CO3: (1.00 g) / (138.21 g/mol) = 0.00724 mol K2CO3 Moles of K: 2 x 0.00724 mol = 0.01448 mol

Determine which compound has the greatest number of potassium ions

Compare the number of moles of potassium ions calculated in step 3 to determine which compound contains the greatest number of potassium ions when dissolved in water. a. KCl: 0.01341 mol b. KClO3: 0.00816 mol c. K3PO4: 0.01414 mol d. KNO3: 0.00989 mol e. K2CO3: 0.01448 mol The compound with the greatest number of potassium ions is potassium carbonate (K2CO3) with 0.01448 moles of potassium ions. Therefore, the correct answer is e. potassium carbonate.

Key concepts

Molar Mass

Understanding molar mass is essential in stoichiometry when comparing the amount of a substance in moles. Molar mass is the mass of one mole of a chemical compound, usually expressed in grams per mole (g/mol). It's calculated by adding up the atomic masses of all the atoms in a molecule. For instance, for potassium chloride (KCl), the molar mass is calculated by adding the atomic mass of potassium (39.10 g/mol) and the atomic mass of chlorine (35.45 g/mol), totaling 74.55 g/mol.
Molar mass helps us convert between grams and moles. For example, if you have 1 gram of KCl, dividing by its molar mass (74.55 g/mol) gives you the number of moles of KCl, which is a key step for finding the number of ions in a solution.

Ions in Solution

When a compound dissolves in water, it dissociates into its constituent ions. This is especially true for ionic compounds. The number of ions released depends on the formula of each compound. For instance, each molecule of KCl dissociates into one potassium ion (K⁺) and one chloride ion (Cl⁻). However, for potassium phosphate (K3PO4), each molecule dissociates into three potassium ions (3 K⁺) and one phosphate ion (PO₄³⁻). This dissociation is crucial in determining which compound provides more potassium ions in solution.
Knowing the dissociation is particularly useful when evaluating which compound yields the greatest number of a specific ion, like potassium, in a stoichiometric problem. The more complex the compound, typically the more ions it may release into solution, impacting the calculation of the total moles of ions available.

Chemical Compounds

Chemical compounds are composed of two or more different elements directly bonded together. They are represented by chemical formulas that denote the types and numbers of atoms in a molecule. The chemical formula is critical in determining both the molar mass and how a compound dissociates in solution.
For example, potassium chlorate (KClO3) contains potassium, chlorine, and oxygen. Its formula highlights how one potassium ion and three oxygen atoms are bound to one chlorine atom.

• KClO3 dissociates to form one K⁺ ion and one ClO₃⁻ ion when dissolved in water.
• Formulas also help calculate the compound's molar mass, influencing stoichiometric calculations.

Understanding chemical compounds involves knowing their physical and chemical structure, which directly affects how they interact with other substances.

Potassium Compounds

Potassium compounds are an important group of chemical compounds. They are known for containing potassium ions and are often studied for their behavior in solutions. Each compound can be identified by its specific chemical formula which determines its properties and how it behaves in a reaction or solution.
Consider potassium carbonate (K2CO3) and potassium nitrate (KNO3).

• Potassium carbonate releases two potassium ions when dissolved in water, making it effective in solutions where higher K⁺ concentrations are desired.
• Potassium nitrate, commonly used in fertilizers, releases one potassium ion and is important in agricultural chemistry.

Knowing various potassium compounds' properties helps predict their roles in chemical processes, like reactions involving mineral fertilizers or those used in laboratory settings to introduce potassium ions. Each compound’s unique combination of elements defines its functionality and application.