What is the minimum weighable amount that a Class A balance can accurately measure?

What is the minimum weighable amount that a Class A balance can accurately measure?

• A. 60 mg
• B. 120 mg
• C. 10 g
• D. 1 g

Answer: (B)

The key idea is understanding the smallest mass a Class A analytical balance can weigh accurately. These balances are highly sensitive, but their accuracy is limited by factors like readability, draft, and calibration. For a Class A balance, reliable measurements start at about 120 mg; masses smaller than this can be affected by noise and environmental factors, making the result not trustworthy. Therefore, 120 mg is the minimum weighable amount that ensures an accurate, repeatable reading. Masses larger than 120 mg are doable, but the question asks for the smallest reliable weight. Hence 120 mg is the best answer.

The key idea is understanding the smallest mass a Class A analytical balance can weigh accurately. These balances are highly sensitive, but their accuracy is limited by factors like readability, draft, and calibration. For a Class A balance, reliable measurements start at about 120 mg; masses smaller than this can be affected by noise and environmental factors, making the result not trustworthy. Therefore, 120 mg is the minimum weighable amount that ensures an accurate, repeatable reading. Masses larger than 120 mg are doable, but the question asks for the smallest reliable weight. Hence 120 mg is the best answer.