Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more...

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Gravimetric Analysis

Transcript of Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more...

Page 1: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Gravimetric Analysis

Page 2: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Quantitative Analysis

• Process of determining how much of one or more constituents are present in a sample

• Two Types of Quantitative Analysis:1) Gravimetric Analysis – Uses weights2) Volumetric Analysis – Uses volumes

Page 3: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Gravimetric Analysis

• Dissolves the sample• Precipitates out one of the constituents• Collects and weighs the precipitate• Determines the weight of the constituent• Calculates the percent of the constituent in

the original sample

Page 4: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Example

• A unknown chloride salt of mass 0.1567g is dissolved in water. Silver nitrate is added and 0.2516g of AgCl precipitate is formed. What is the percent of chlorine in the original sample?

Page 5: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Statistics

• Used to analyze results• Experiments are repeated several times • It is important that the results are repeatable

and not just random (there is precision)

Page 6: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Mean

• Average of the measurements

mean = sum of results number of results

Page 7: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Deviation

• How much a result is different from the mean

d = result - mean

Page 8: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Standard Deviation

• Gives an indication of the precision of the measurement

s.d. = sum of the squares of deviations number of results - 1

Page 9: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

Example

An experiments results are 1, 3, and 5. Calculate the mean, the deviations from the mean, and the standard deviation.

Page 10: Gravimetric Analysis. Quantitative Analysis Process of determining how much of one or more constituents are present in a sample Two Types of Quantitative.

What does it tell you?

• Any result more than two standard deviations from the mean is meaningless and should be discarded