ACS Quantitative Chemical Analysis Final Exam

a portion of a sample

aliquot

a solution whose composition is known accurately

standard solution

the substance of interest in a chemical analysis, the substance being measured

analyte

a liquid remaining above a solid after precipitation

supernatant

a suspension of a solid in a solvent

slurry

in water

aqueous

List the 7 steps of the chemical analysis

1. Formulate the question

2. Select an analytical procedure

3. Obtain a sample

4. Prepare the sample

5. Sample analysis

6. Report results

7. Draw conclusions

a portion of material used for analysis

sample

all substances found within a material

matrix

Identify the sample and analyte in the following scenarios

1. Determination of the lead content in paint

2. Analysis of the nitrate content of soil near a local water source

3. Measurement of the citric acid found in a lime wedge

1. analyte: lead

sample: paint chips

2. analyte: soil

sample: nitrate

3. analyte: citric acid

sample: lime wedge

How is the mass of the 10.0 mL of distilled water you measured at 11ºC different from the mass of the 10.0 mL of distilled water at 20º C?

IF the masses are different, is the error in mass due to the temperature difference a systematic or random error?

It is greater than the mass of water at 20ºC

systematic error

A consistent, reproducible error that can be detected and corrected

systematic error

The result of uncontrollable variables in a measurement and has an equal chance of being positive or negative

random error

Report to the proper amount of sig figs

1. log(9.2x10⁷)

2. 10¹.²⁸

1. 7.96

2. 19

What is the relationship between the standard deviation and the precision of a procedure?

The smaller the standard deviation, the greater the precision

What is the relationship between the standard deviation and the accuracy of a procedure?

There is no relationship between standard deviation and accuracy

90% confidence interval

mean ± (t)(s) ÷ √n

Grubbs test

‖questionable value - mean‖ ÷ standard deviation

if Gcalc is > Gtable then the value should be rejected

Ionic strength 0.10 M NaOH

m = 1/2 {[Na⁺][+1]² + [OH⁻][-1]²} = 1/2 {[0.1M][1] + [0.1M][1] = 0.1 M