ch 1 Conversions & Sig Figs

CHM 151 – Conversions & Sig Figs Quiz

Significant Figures Quiz
  • Viruses rarely exist in isolation; they are usually attached to something in the air, making them larger than their individual size when found in nature.
Question 1
  • Which measurement has been expressed to four significant figures?
    • a. 0.0020 mm
    • b. 30.00 mm
    • c. 0.00402 mm
    • d. 402.10 mm
  • Answer: b. 30.00 mm
Question 2
  • How many significant figures are in the measurement “170.040”?
    • a. 3
    • b. 4
    • c. 5
    • d. 6
  • Answer: d. 6
Question 3

  • Answer the following with correct significant figures:

    97.2×1.025×12=97.2 \times 1.025 \times 12 =

    • a. 11.95
    • b. 1195.56
    • c. 1200
    • d. 12

  • Answer: c. 1200 (because 12 has the least number of significant figures, which is 1)

Question 4

  • Answer the following with correct significant figures:

    206.3+5.64206.3 + 5.64

    • a. 210
    • b. 212
    • c. 211.9
    • d. 211.94

  • Answer: c. 211.9 (because 206.3 has the least number of decimal places, which is 1)

Question 5
  • Use proper significant figures to report the amount pictured in the instrument.
    • a. 43 mL
    • b. 43.1 mL
    • c. 40 mL
    • d. 43.10 mL
  • Answer: b. 43.1 mL
Coronavirus and Face Masks
  • In the human body, the coronavirus latches its spiky surface proteins to receptors on healthy cells, especially in the lungs.
  • Once attached to specific ACE2 receptors, the virus takes command of healthy cells and eventually kills them.
  • During the pandemic, scientists and the CDC recommended wearing face masks as a form of protection against the virus.
Question 6
  • The Covid-19 virus has a diameter of approximately 2.5×10−82.5 \times 10^{-8} cm. Convert this diameter to micrometers (μ\mum). Show your work.
  • Solution:
    (2.5×10−8cm)×(1m100cm)×(106μm1m)=2.5×10−4μm(2.5 \times 10^{-8} cm) \times (\frac{1 m}{100 cm}) \times (\frac{10^6 \mu m}{1 m}) = 2.5 \times 10^{-4} \mu m or 0.00025 μ\mum
Question 7

  • Holes in the fabric of an N95 mask are 300 nm in diameter. Can the Covid-19 virus fit through these? Explain.

  • Solution 1:

    300nm×(1m109nm)×(106μm1m)=0.3μm300 nm \times (\frac{1 m}{10^9 nm}) \times (\frac{10^6 \mu m}{1 m}) = 0.3 \mu m

    • Yes, 0.3 > 0.00025, so the virus can fit.

  • Solution 2:

    0.00025μm×(1m106μm)×(109nm1m)=0.25nm0.00025 \mu m \times (\frac{1 m}{10^6 \mu m}) \times (\frac{10^9 nm}{1 m}) = 0.25 nm

    • Yes, 300 nm > 0.25 nm, so the virus can fit.