Question

Identify each of the following experimental occurrences as contributing to systematic error “S”, random error “R”, both types of error “B”, or neither (does not cause error) “N” Write the code letters S, R, B or N, as appropriate, in the space beside the phrase.

____ reading a meniscus from above the plane of the calibration mark

____ reading a meniscus in the plane of the calibration mark, but with limits of human visual acuity

____ transferring analyte solution from one vessel to another, to varying degrees of completeness

____ loss of varying amounts of analyte during transfer from sample vials to beakers

____ small up-and-down variations in room temperature during weighing and solution prep

____ weighing a sample directly from the oven without cooling it

____ incomplete drying of a primary standard, prior to weighing a sample

____ completely cooling a weigh bottle in a desiccator prior to weighing a sample

____ using a glove or a paper loop to handle a weigh bottle between the first and second weighings

____ incompletely dissolving the sample in a volumetric flask prior to removing an aliquot for analysis

Please explain Why i want to understand

Answer 1

Let's go to the basic definition of the Ransom and Systematic errors:

Random error: It is always present in a measurement. It is caused by inherently unpredictable fluctuations in the readings of a measurement apparatus or in the experimenter's interpretation of the instrumental reading.

Random errors in experimental measurements are caused by unknown and unpredictable changes in the experiment. These changes may occur in the measuring instruments or in the environmental conditions.

Examples of causes of random errors are:

• electronic noise in the circuit of an electrical instrument,
• irregular changes in the heat loss rate from a solar collector due to changes in the wind.

Systematic errors :Systematic errors in experimental observations usually come from the measuring instruments. They may occur because:

• there is something wrong with the instrument or its data handling system, or
• because the instrument is wrongly used by the experimenter.

Here we go with our Cases:

1. Reading a meniscus from above the plane of the calibration mark : Here the experimenter is not following systematic process (above the plane of the meniscus) for measuring the reading and there might be fluctuatuion in the meniscus level. Hence Random and systematic error possible.

2.Reading a meniscus in the plane of the calibration mark, but with limits of human visual acuity: no error as this doesnot fall in to any of the above category.

3. Transferring analyte solution from one vessel to another, to varying degrees of completeness: This comes under the Random error as it is assosciated with the liquid solution which bwlongs to the system.

4. Loss of varying amounts of analyte during transfer from sample vials to beakers: This belong to the Random error as well.

5. Small up-and-down variations in room temperature during weighing and solution prep: This clearly a Random error. Changes in the surroundings.

6. Weighing a sample directly from the oven without cooling it: As the process is to weigh after cooling, it is a systematic error as it in the experimenter hands. ans if there is problem with measuring instrument , there is a chance of random error as well

7. incomplete drying of a primary standard, prior to weighing a sample: This belongs to the same case, systematic error and might include Random error.

8.completely cooling a weigh bottle in a desiccator prior to weighing a sample: Here there is only a chance of Random error, if the meauring instrument has a problem.

9 . Using a glove or a paper loop to handle a weigh bottle between the first and second weighingsI: No error. as it is not effecting the measuring substance or instrument in any way.

10 Incompletely dissolving the sample in a volumetric flask prior to removing an aliquot for analysis: Systematic error as there is a mistake in the process by experimenter.