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Question

Difficulty: EasyErrors in Measurement and Significant Figures

A student records the mass of a chemical sample using a digital balance as 0.02050 kg0.02050\text{ kg}. How many significant figures are contained in this measurement?

  1. A
    3
  2. 4Answer
  3. C
    5
  4. D
    2

Answer

4 significant figures
In the measurement 0.02050 kg0.02050\text{ kg}, the leading zeros (0.00.0) are placeholders and do not count as significant. The non-zero digits (22 and 55), the captive zero between them, and the trailing zero following the decimal point are all significant. This gives a total of four significant figures.

Step-by-Step Solution

1
Identify and evaluate leading zeros in 0.02050 kg0.02050\text{ kg}.
The zeros before the digit '2' (0.00.0) are leading zeros.
Leading zeros serve only as decimal placeholders and are never significant.
2
Identify non-zero digits and zeros between non-zero digits.
The digits '2' and '5' are non-zero, and the zero between them is a captive zero.
All non-zero digits and zeros trapped between non-zero digits are always significant.
3
Evaluate the trailing zero.
The zero after '5' is a trailing zero in a decimal number.
Trailing zeros to the right of a decimal point indicate measurement precision and are significant.
4
Sum the total number of significant figures.
Digits '2', '0', '5', and '0' give a total of 4 significant figures.
Combining two non-zero digits, one captive zero, and one trailing decimal zero gives four significant figures.

Key Concept

Rules for counting significant figures in physical measurements
Estimated Time:45s
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Topics

Errors in Measurement and Significant Figures

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