Primary Standards in Chemistry

The video discusses primary standards, focusing on their importance in creating standard solutions. It outlines undesirable properties like being hydroscopic or deliquescent, and desirable properties such as purity, stability, and high molar mass. Examples of poor primary standards include sodium hydroxide and hydrochloric acid, while good examples are sodium carbonate and potassium dichromate.

What is the main purpose of a primary standard in chemistry?

• To absorb water from the atmosphere

• To create a solution with a known concentration

• To decompose into other substances

• To react with carbon dioxide

Which property is undesirable for a primary standard due to its ability to absorb moisture?

• Hygroscopic

• Stable

• High molar mass

• Pure

Why is a high molar mass preferred in a primary standard?

• It decreases the error in mass measurement

• It reduces the substance's stability

• It makes the substance more reactive

• It increases the error in mass measurement

Which of the following is NOT a reason why sodium hydroxide is unsuitable as a primary standard?

• It is deliquescent

• It is not pure

• It reacts with carbon dioxide

• It is a gas at room temperature

What happens to potassium manganate over time, making it unsuitable as a primary standard?

• It absorbs water and becomes diluted

• It decomposes into manganese dioxide

• It remains stable and unchanged

• It reacts with acids

What is the main challenge with using hydrochloric acid as a primary standard?

• It is highly stable

• It is a gas and difficult to handle

• It does not react with bases

• It is a solid at room temperature

Which substance is considered a good primary standard for acid-base titrations?

• Sodium carbonate

• Hydrochloric acid

• Sodium hydroxide

• Potassium manganate

What is a key feature of potassium dichromate that makes it a good primary standard?

• It is a strong oxidizer and stable

• It is highly reactive

• It is unstable

• It decomposes easily

Which ion is commonly used in redox titrations due to its stability?

• Chloride ion

• Oxalate ion

• Hydroxide ion

• Carbonate ion

Why is sodium oxalate used in redox titrations?

• It absorbs water

• It is a stable reducing agent

• It is a strong acid

• It is unstable