Lead(II) chloride

Key takeaways

Lead(II) chloride belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lead(II) chloride to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lead(II) chloride from memory before moving on to harder problems.

Reference excerpt

Lead(II) chloride (PbCl2) is an inorganic compound which is a white solid under ambient conditions. It is poorly soluble in water. Lead(II) chloride is one of the most important lead-based reagents. It also occurs naturally in the form of the mineral cotunnite.

Structure and properties In solid PbCl2, each lead ion is coordinated by nine chloride ions in a tricapped triangular prism formation — six lie at the vertices of a triangular prism and three lie beyond the centers of each rectangular prism face. The 9 chloride ions are not equidistant from the central lead atom, 7 lie at 280–309 pm and 2 at 370 pm. PbCl2 forms white orthorhombic needles.

In the gas phase, PbCl2 molecules have a bent structure with the Cl–Pb–Cl angle being 98° and each Pb–-Cl bond distance being 2.44 Å. Such PbCl2 is emitted from internal combustion engines that use ethylene chloride-tetraethyllead additives for antiknock purposes. PbCl2 is sparingly soluble in water, solubility product Ksp = 1.7×10−5 at 20 °C. It is one of only 5 commonly water-insoluble chlorides, the other 4 being thallium(I) chloride, silver chloride (AgCl) with Ksp = 1.8×10−10, copper(I) chloride (CuCl) with Ksp = 1.72×10−7 and mercury(I) chloride (Hg2Cl2) with Ksp = 1.3×10−18.

Synthesis Solid lead(II) chloride precipitates upon addition of aqueous chloride sources (HCl, NaCl, KCl) to aqueous solutions of lead(II) compounds, such as lead(II) nitrate and lead(II) acetate:

Pb(NO3)2 + 2 HCl → PbCl2(s) + 2 HNO3 It also forms by treatment of basic lead(II) compounds such as Lead(II) oxide and lead(II) carbonate. Lead dioxide is reduced by chloride as follows:

PbO2 + 4 HCl → PbCl2(s) + Cl2 + 2 H2O It also formed by the oxidation of lead metal by copper(II) chloride:

Pb + CuCl2 → PbCl2 + Cu Or most straightforwardly by the action of chlorine gas on lead metal:

Pb + Cl2 → PbCl2

Reactions Addition of chloride ions to a suspension of PbCl2 gives rise to soluble complex ions. In these reactions the additional chloride (or other ligands) break up the chloride bridges that comprise the polymeric framework of solid PbCl2(s).

PbCl2(s) + Cl− → [PbCl3]−(aq) PbCl2(s) + 2 Cl− → [PbCl4]2−(aq) PbCl2 reacts with molten NaNO2 to give PbO:

PbCl2(l) + 3 NaNO2 → PbO + NaNO3 + 2 NO + 2 NaCl PbCl2 is used in synthesis of lead(IV) chloride (PbCl4): Cl2 is bubbled through a saturated solution of PbCl2 in aqueous NH4Cl forming [NH4]2[PbCl6]. The latter is reacted with cold concentrated sulfuric acid (H2SO4) forming PbCl4 as an oil. Lead(II) chloride is the main precursor for organometallic derivatives of lead, such as plumbocenes. The usual alkylating agents are employed, including Grignard reagents and organolithium compounds:

2 PbCl2 + 4 RLi → R4Pb + 4 LiCl + Pb 2 PbCl2 + 4 RMgBr → R4Pb + Pb + 4 MgBrCl 3 PbCl2 + 6 RMgBr → R3Pb-PbR3 + Pb + 6 MgBrCl These reactions produce derivatives that are more similar to organosilicon compounds, i.e. that Pb(II) tends to disproportionate upon alkylation. PbCl2 can be used to produce PbO2 by treating it with sodium hypochlorite (NaClO), forming a reddish-brown precipitate of PbO2.

Uses Molten PbCl2 is used in the synthesis of lead titanate and barium lead titanate ceramics by cation replacement reactions: x PbCl2(l) + BaTiO3(s) → Ba1−xPbxTiO3 + x BaCl2 PbCl2 is used in production of infrared transmitting glass, and ornamental glass called aurene glass. Aurene glass has an iridescent surface formed by spraying with PbCl2 and reheating under controlled conditions. Stannous chloride (SnCl2) is used for the same purpose. Pb is used in HCl service even though the PbCl2 formed is slightly soluble in HCl. Addition of 6–25% of antimony (Sb) increases corrosion resistance. A basic chloride of lead, PbCl2·Pb(OH)2, is known as Pattinson's white lead and is used as pigment in white paint. Lead paint is now banned as a health hazard in many countries by the White Lead (Painting) Convention, 1921. PbCl2 is an intermediate in refining bismuth (Bi) ore. The ore containing Bi, Pb, and Zn is first treated with molten caustic soda to remove traces of arsenic and tellurium. This is followed by the Parkes process to remove any silver and gold present. There are now Bi, Pb, and Zn in the ore. At 500 °C, it receives treatment from Cl2 gas. First, ZnCl2 forms and is excreted. Pure Bi is left behind after PbCl2 forms and is eliminated. Lastly, BiCl3 would form.

Toxicity Like other soluble lead compounds, exposure to PbCl2 may cause lead poisoning.

References

External links

IARC Monograph: "Lead and Lead Compounds" IARC Monograph: "Inorganic and Organic Lead Compounds" National Pollutant Inventory – Lead and Lead Compounds Fact Sheet Case Studies in Environmental Medicine – Lead Toxicity Archived 2016-02-04 at the Wayback Machine ToxFAQs: Lead

Illustrations

Worked examples

Example 1 — a first encounter with Lead(II) chloride

Start with the simplest possible case. Write down what Lead(II) chloride claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lead(II) chloride before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lead(II) chloride ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lead(II) chloride

In research: Lead(II) chloride appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lead(II) chloride in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lead(II) chloride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chlorides, IARC Group 2A carcinogens, Lead(II) compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Lead(II) chloride outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Lead(II) chloride in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lead(II) chloride means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lead(II) chloride out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lead(II) chloride in simple terms?

Lead(II) chloride (PbCl2) is an inorganic compound which is a white solid under ambient conditions. It is poorly soluble in water.

Why does Lead(II) chloride matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lead(II) chloride?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lead(II) chloride.