Measurements and Uncertainties

Which of the following is a correct statement about systematic errors?

• They arise due to incorrect judgment of a measurement.

• Their magnitude depends on the experimenter’s skill.

• They are consistent in magnitude.

• They occur as a result of a person’s inability to perform the experiment correctly.

• All of the above

Accuracy

– How close a measurement is to _________________________________________

Scenario :

A group is trying to find the volume of a given liquid. To do this, they are using a graduated cylinder that is graduated by milliliters. They pour the substance into the graduated cylinder and take their reading. One group member says there are 25.5mL. Another group member says it’s 25mL exactly and a third group member says they think it’s 25.6mL. What are the possible sources of error for this measurement?

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Mohammed used a 50.0 mL burette to add the KMnO_{4 (aq)} to the H₂C₂O_{4 (aq)} until a faint lavender color was observed in the flask, an indication that the end point of the titration had been reached. The initial and final volume readings of the solution in the burette are shown below. Write down the initial reading and the final reading with its uncertainty value.

• Initial Reading: 46.60 + 0.01 mL

• Initial Reading: 3.40 + 0.01 mL

• Final Reading: 20.44 + 0.01 mL

• Final Reading: 29.56 + 0.01 mL

The density of ethanol is 0.802 g/mL. How much in grams does 9.85 x 10^-2 L of this mass?

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What is the density in g/mL of a substance that masses 0.987 kg and has a volume of 4.52 x 10² mL?

• 2180 g/mL

• 2.18 g/mL

• 21.8 g/mL

• 218.0 g/mL