Problem 17 - Chemistry in 30 days

Question

Identify the incorrect statement regarding mercuric chloride (a) gives scarlet precipitate with \(\mathrm{KI}\) (b) is poisonous, and egg white is used as the antidote. (c) more soluble in cold water than hot water (d) it absorbs gaseous ammonia

Step-by-Step Solution

Answer

(c) More soluble in cold water than hot water is incorrect.

Step 1: Review Each Statement

To find the incorrect statement, we need to examine each option based on the chemical properties of mercuric chloride.

Step 2: Analyze Statement (a)

Mercuric chloride reacts with \(\mathrm{KI}\) to give a scarlet precipitate of mercuric iodide \(\text{HgI}_2\), which is true.

Step 3: Analyze Statement (b)

Mercuric chloride is indeed poisonous, and it is known that proteins like those in egg whites can precipitate and thereby neutralize mercury ions, acting as an antidote. This statement is true.

Step 4: Analyze Statement (c)

Generally, the solubility of most substances increases with temperature. Hence, it is unusual for mercuric chloride to be more soluble in cold water than hot. This statement is likely incorrect.

Step 5: Analyze Statement (d)

Mercuric chloride can absorb gaseous ammonia, forming a white compound known as mercuric amidochloride. This statement is true.

Key Concepts

Poisonous Substances

Mercuric chloride is a highly toxic compound, making it a notable example of a poisonous substance. Its toxicity arises from the mercury ions it contains, which are harmful to biological systems. This characteristic of being poisonous demands extreme care when handling it. However, if ingested, one can use protein-rich substances such as egg white as an antidote.

• The egg white works by binding to the mercury ions, thereby neutralizing them and preventing further absorption into the body.
• This method exploits the chemistry between proteins and mercury ions, showing how chemicals and everyday compounds can interact in life-saving ways.

Thus, the knowledge of both its toxicity and the simple antidote can be helpful in emergencies.

Solubility

Solubility is a critical property of substances, and understanding it helps in predicting how substances behave in different conditions. Typically, the solubility of a solid in a liquid increases with temperature. However, mercuric chloride does not follow this trend, which can be a point of confusion for many students.

• In most cases, as the temperature increases, substances become more soluble.
• Yet, with mercuric chloride, there's an exception as noted in the incorrect statement; it doesn't conform to this common rule.

This peculiarity makes it an interesting topic, challenging our general understanding and prompting deeper exploration into the complete solubility behavior of mercuric chloride.

Chemical Reactions with KI

Mercuric chloride reacts with potassium iodide (KI) to form a scarlet precipitate, mercuric iodide ( ext{HgI}_2 ). This reaction is a classic demonstration in chemistry, highlighting important aspects of reaction observation and analysis.

• Upon mixing with ( ext{KI} ), you will notice a vivid red or scarlet precipitate forming.
• This reaction is reliably used in laboratory settings to demonstrate chemical precipitation.

Understanding this reaction provides insights into precipitation reactions, where an insoluble solid ( ext{precipitate} ) forms from the mixing of two solutions.

Ammonia Absorption

The ability of mercuric chloride to absorb gaseous ammonia is another intriguing property. When it interacts with ammonia, a chemical change occurs, leading to the formation of a new compound known as mercuric amidochloride.

• This property is an example of how mercuric chloride engages with gases, facilitating a chemical change.
• The process results in the formation of a white compound, manifesting as a visible reaction product.
• Such reactions are crucial in understanding how gaseous interactions can dramatically change the properties and characteristics of a compound.

This concept illustrates the interaction between a solid and a gas, broadening the understanding of chemical interactions beyond liquid solutions.