Question

Compounds of lead have been used throughout the ages before anyone realized lead's toxicity. (a) Flake white was a white pigment used by Renaissance artists, which was composed of a combination of lead(II) carbonate and lead(II) hydroxide. What are the correct chemical formulas for these two compounds? (b) Lead(II) oxide has been added to glass to make crystal that glistens beautifully. When wine is stored in a crystal decanter, the lead slowly leaches out making lead(II) acetate, which is also known as the sugar of lead. It gives the wine a very sweet flavor but is unfortunately also very toxic. Write the correct chemical formulas for these two compounds.

Short answer

The correct chemical formulas are: lead(II) carbonate - PbCO3, lead(II) hydroxide - Pb(OH)2, lead(II) oxide - PbO, and lead(II) acetate - Pb(C2H3O2)2.

Step-by-step solution

Identify the Lead Ion

To write the correct chemical formulas for compounds containing lead(II), recognize that the lead(II) ion has a +2 charge, represented as Pb^{2+}.

Determine the Chemical Formulas for Lead Compounds

Using the ion charges, combine lead(II) with the carbonate ion (CO3^{2-}) and hydroxide ion (OH^-) to obtain the correct formulas. Lead(II) carbonate is PbCO3 since the charges of lead and carbonate balance out. For lead(II) hydroxide, two hydroxide ions are needed to balance the +2 charge of lead(II), giving us Pb(OH)2.

Identify the Acetate Ion

Acetate is a polyatomic ion with the formula CH3COO^- or C2H3O2^- and a -1 charge.

Write the Formula for Lead(II) Oxide

Combine the lead(II) ion with oxygen, which commonly has a -2 charge (O^{2-}), to get PbO for lead(II) oxide.

Write the Formula for Lead(II) Acetate

Since acetate has a -1 charge and lead has a +2 charge, two acetate ions are required to balance one lead ion, resulting in Pb(CH3COO)2 or Pb(C2H3O2)2 for lead(II) acetate.

Key concepts

Lead Toxicity

The dangers of lead have become well understood, with modern science highlighting lead toxicity as a critical health issue. Prolonged exposure to lead compounds can cause a variety of health problems, including neurological deficits, anemia, kidney damage, and issues with the reproductive system. In children, these effects are particularly concerning, as lead can severely affect mental and physical development.

Despite its utility in various industries, conscientious handling and proper education about the risks of lead are essential. The presence of lead in old paints, pipes, and other household items is a significant concern, and there's a global push to replace and mitigate lead in environments, especially those frequented by children.

Lead Compounds in History

Throughout history, lead compounds have been crafted for their physical properties without an understanding of their toxicological effects. For example, lead(II) acetate, historically known as sugar of lead, was used as a sweetener and wine preservative. This compound's sweetness belies its poisonous nature. Lead-based cosmetics, pottery glazes, and piping were other common uses.

As an educational note, it is crucial to recognize the dual nature of many chemical compounds; understanding context in history and the progression in knowledge about their effects is an important aspect of chemical education.

Chemical Formula Writing

Writing chemical formulas accurately is a fundamental skill in chemistry. It involves pairing a cation (positively charged ion) and an anion (negatively charged ion) in a ratio that results in a neutral compound. This process requires knowledge of the ionic charges involved and the principle of charge balance: The total positive charge must equal the total negative charge.

The chemical formula for a compound not only denotes the elements present but also provides critical information about their proportions. For example, lead(II) hydroxide, Pb(OH)2, indicates one lead ion for every two hydroxide ions, maintaining charge balance. Emphasizing the significance of balancing charges in chemical formula writing is helpful for students to grasp the nuances behind the compositions of chemical compounds.

Polyatomic Ions

A polyatomic ion is a charged entity composed of two or more atoms covalently bonded. These ions are prevalent in many compounds and are essential to understand in chemistry. For instance, the hydroxide ion (OH^-) and the carbonate ion (CO3^{2-}) are both polyatomic ions. They have distinct structures and charges that must be recognized when determining the correct formulas for compounds containing them.

When writing chemical formulas with polyatomic ions, use parentheses to denote the desired number of the ions if there is more than one ion required to balance the compound's charge. As an example, in lead(II) acetate, Pb(CH3COO)2, parentheses enclose the acetate ion to indicate that two of these ions are combined with a single lead(II) ion.

Ionic Charges in Compounds

Understanding ionic charges is critical when constructing chemical formulas. Ions are atoms or groups of atoms with a net electric charge due to the loss or gain of electrons. Metals typically form cations by losing electrons and nonmetals form anions by gaining electrons. The charge on an ion is denoted by a superscript, such as Pb^{2+} for a lead(II) cation with a +2 charge.

In compounds like PbCO3 or PbO, it's essential to balance the total positive and negative charges. Lead, being a metal, often forms compounds by donating electrons and thus carries a positive charge in its ionic state. Helping students understand that ionic charges guide the formation of compounds can demystify many aspects of chemical reactions and compound structures.