CHEM 300 EXAM 1

Question 1

parallax

Answer 1

error that occurs when your eye is not at the meniscus

Question 2

how do you take sig figs for log?

Answer 2

answer has the same number of sig figs in mantissa (after decimal) as the whole number does that you’re taking the log of

Question 3

what is human error

Answer 3

systematic/determinate

Question 4

what is random error

Answer 4

indeterminate; limited by precision of tools

Question 5

how to propagate when adding and substracting?

Answer 5

use absolute error

Question 6

how to propagate when multiplying and dividing?

Answer 6

use relative error (%)

Question 7

calibration curve

Answer 7

prepare serial dilutions of standard
record signal for each dilution multiple times
plot signal vs concentration
use LINEST
measure signal for unknown
use: when sample matrix is clean, instrument response is linear, and sample prep is easy

Question 8

standard addition

Answer 8

use known quantities of analyte added to unknown to find the concentration of unknown
record unknown signal multiple times and add known amount of standard and record signal and use equation
use: when sample matrix is dirty or unknown, instrument response is linear and sample prep is straightforward

Question 9

multiple additions

Answer 9

in case analysis does consume some sample we can make multiple solutions with different additions but equal volumes, this way if there is interference and sample was not prepared properly perhaps we can account for it

Question 10

internal standard

Answer 10

known amount of compound is different from analyte and signal from analyte is compared to signal from standard
use: when sample matrix is clean or dirty and instrument response is fairly equal and sample prep is harder