Introduction to chemical analysis Flashcards
What are the two main types of methods in quantitative analysis?
Classical Methods and Instrumental Methods
Classical Methods include volumetric analysis; Instrumental Methods use specialized equipment.
Define precision in the context of chemical analysis.
Repeating the experiment yields measurements that are the same or similar.
What is accuracy in measurements?
Closeness of a measurement to the true value.
What are determinate errors?
Systematic errors that affect accuracy and can be identified and corrected.
List the three types of determinate errors.
- Instrumental Error
- Method Error
- Personal Error
What are indeterminate errors?
Random errors that affect precision and cannot be corrected.
How can random error be reduced?
Repeating the experiment to calculate the mean.
What is the spread on a Gaussian Distribution?
Spread due to random error; 95% of readings are within 2 standard deviations of the mean.
What are the 3 Student’s T-tests
Test comparing measured and true values.
Test comparing replicate measurements
Difference test comparing when two different methods are used to make SINGLE MEASUREMENTS on different samples
What is the decision rule for comparing experimental and true mean values using Student’s T-Test?
If t-calc < t-table → Sample and true values are similar; If t-calc > t-table → Sample and true values are very different.
What does the F-Test compare?
The precision of measurements.
What is the decision rule for the F-Test?
If F-calc > F-table → The difference is significant.
How is the Q-Test used to detect outliers?
Calculate gaps and compute Q = Gap / Range.
What is the decision rule for the Q-Test?
If Q-calc > Q-table → The value is an outlier.
What happens to sample mean and sample standard deviation as N approaches infinity?
Sample mean approaches population mean (μ) and sample standard deviation approaches population standard deviation (σ).
How should significant figures be handled in addition and subtraction?
Follow decimal places.
How should significant figures be handled in multiplication and division?
Follow significant figures.
What is a Certified Reference Material (CRM)?
A commonly manufactured material with a known composition, analyzed by multiple laboratories.
What must a CRM be certified for?
The analyte being used.
