Question

count the significant digits in each of these measurements: measurement number of significant digits 0.004200 j 1.8×10^{-3} ml - 5.0×10^{-3} kj/mol 84400. kg

Explanation:

Step1: Recall significant - digit rules

Non - zero digits are always significant. Leading zeros (zeros before non - zero digits) are not significant. Trailing zeros (zeros after non - zero digits) are significant if there is a decimal point.

Step2: Analyze 0.004200 J

The leading zeros are not significant. The non - zero digits 4, 2 and the two trailing zeros are significant. So there are 4 significant digits.

Step3: Analyze 1.8×10⁻³ mL

In scientific notation, only the digits in the coefficient (1.8) are considered for significant digits. So there are 2 significant digits.

Step4: Analyze - 5.0×10⁻³ kJ/mol

The coefficient is 5.0. The zero after 5 is significant because of the decimal point. So there are 2 significant digits.

Step5: Analyze 84400. kg

The decimal point makes the trailing zeros significant. So there are 5 significant digits.

Answer:

0.004200 J: 4
1.8×10⁻³ mL: 2

• 5.0×10⁻³ kJ/mol: 2

1. kg: 5