CHEMISTRY_TOPIC 4 & 5

A scientist measures the concentration of pollutants in a river and records the value as 0.00560 mg/L. How many significant figures are in this measurement?

• 2

• 3

• 4

• 5

A researcher reports that the amount of plastic waste in a sample of ocean water is 8500 kg. The value is expressed as 8.5 × 10³ kg. How many significant figures are in this value?

• 1

• 2

• 3

• 4

Which of the following values does not contain five (5) significant figures?

• 39.005 m

• 500.02 m

• 1234.0 m

• 0.1003 m

An environmental engineer measures the level of dissolved oxygen in a lake to be 0.000123589 mg/L. Round off the value into two and four significant figures, respectively.

• 0.00013 mg/L,

  0.000124 mg/L

• 0.0001 mg/L,

  0.000120 mg/L

• 0.00012 mg/L,

  0.0001235 mg/L

• 0.00012 mg/L, 0.0001236 mg/L

When adding or subtracting measured numbers, what should the answer's decimal places be based on?

• The average of all measurements' decimal places.
• The measurement with the highest decimal places.
• The measurement with the fewest decimal places.
• The measurement with the largest value.

If you add 3.456 and 1.2, how many decimal places should the answer have?

• 2
• 4
• 1
• 3

Which of the following additions correctly follows the rule for decimal places?

• • 2.345 + 4.2 = 6.545

• • 2.345 + 4.2 = 6.5

• • 2.3 + 4.2 = 6.55

• • 2.3 + 4.2 = 6.5

When multiplying or dividing measured numbers, how should the number of significant figures in the result be determined?

• By the largest number of significant figures in the measured numbers.

• By the smallest number of significant figures in the measured numbers.

• By the average number of significant figures in the measured numbers.

• By the number of decimal places in the measured numbers.

In a study of greenhouse gas emissions, a researcher calculates the CO₂ emissions as 5.678 kg and 2.3 kg. What is the result of dividing these values?

• 2.5
• 2.47

• 3

• 2.468

What is the product of (12.5 cm) (4.60 cm) (3.271 cm) applying the rules in multiplying measured numbers?

• 188 cm³

• 188.08 cm³

• 1.88 x 10² cm³

• 188.0 cm³