chemistry

Lead hydrogen arsenate

Lead hydrogen arsenate is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lead hydrogen arsenate rather than just read about it. In short: Lead hydrogen arsenate, also called lead arsenate, acid lead arsenate or LA, chemical formula PbHAsO4, is an inorganic insecticide formerly used to control pests including gypsy moth, potato beetle and rats. Lead arsenate was the most extensively used arsenical insecticide.

Key takeaways

Lead hydrogen arsenate 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 hydrogen arsenate to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lead hydrogen arsenate from memory before moving on to harder problems.

Reference excerpt

Lead hydrogen arsenate, also called lead arsenate, acid lead arsenate or LA, chemical formula PbHAsO4, is an inorganic insecticide formerly used to control pests including gypsy moth, potato beetle and rats. Lead arsenate was the most extensively used arsenical insecticide. Two principal formulations of lead arsenate were marketed: basic lead arsenate (Pb5OH(AsO4)3, CASN: 1327-31-7) and acid lead arsenate (PbHAsO4). It is now banned for use as a pesticide in countries such as the US and UK as it is considered too toxic and persistent.

Production and structure It is usually produced using the following reaction, which leads to formation of the desired product as a solid precipitate:

Pb(NO3)2 + H3AsO4 → PbHAsO4 +2 HNO3 It has the same structure as the hydrogen phosphate PbHPO4. Like lead sulfate PbSO4, these salts are poorly soluble.

Uses As an insecticide, it was introduced in 1898 used against the gypsy moth in Massachusetts. It represented a less soluble and less toxic alternative to then-used Paris Green, which is about 10x more toxic. It also adhered better to the surface of the plants, further enhancing and prolonging its insecticidal effect. Lead arsenate was widely used in Australia, Canada, New Zealand, US, England, France, North Africa, and many other areas, principally against the codling moth and snow-white linden moth. It was used mainly on apples, but also on other fruit trees, garden crops, turfgrasses, and against mosquitoes. In combination with ammonium sulfate, it was used in southern California as a winter treatment on lawns to kill crab grass seed. The search for a substitute was commenced in 1919, when it was found that its residues remain in the products despite washing their surfaces. Alternatives were found to be less effective or more toxic to plants and animals, until 1947 when DDT was found. US EPA banned use of lead arsenate on food crops in 1988.

Safety LD50 is 1050 mg/kg (rat, oral). Morel mushrooms growing in old apple orchards that had been treated with lead arsenate may accumulate levels of toxic lead and arsenic that are unhealthy for human consumption. Lead arsenate was used as an insecticide in deciduous fruit trees from 1892 until around 1947 in Washington. Peryea et al. studied the distribution of Pb and As in these soils, concluding that these levels were above maximum tolerance levels. This indicates that these levels could be of environmental concern and potentially could be contaminating the groundwater in the area.

Illustrations

Worked examples

Example 1 — a first encounter with Lead hydrogen arsenate

Start with the simplest possible case. Write down what Lead hydrogen arsenate 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 hydrogen arsenate 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 hydrogen arsenate 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 hydrogen arsenate

In research: Lead hydrogen arsenate 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 hydrogen arsenate 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 hydrogen arsenate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arsenates, Hydrogen compounds, Inorganic insecticides, so understanding it makes those chapters shorter.
In everyday life: Look for Lead hydrogen arsenate 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.

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How to study Lead hydrogen arsenate in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lead hydrogen arsenate 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 hydrogen arsenate out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lead hydrogen arsenate in simple terms?

Why does Lead hydrogen arsenate 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 hydrogen arsenate?

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 hydrogen arsenate.