unit 3

Question 1

precision vs accuracy

Answer 1

p: closeness of agreement b/w independent test results
a: closeness of agreement b/w result and true value

Question 2

how does random error occur, how can it be reduced, what does it affect

Answer 2

• caused by uncontrolled variables
• can be reduced by repeated measurements
• affects precision of results

Question 3

how does systematic error occur, how can it be reduced, what does it affect

Answer 3

• caused by poor experiment design, procedure, instrumentation
• cannot be reduced by repeating measurements
• affects accuracy of results

Question 4

what does it mean if experiment is repeatable

Answer 4

if same person does experiment again, they will get same result

Question 5

what does it mean if experiment is reproducible

Answer 5

if several experimenters duplicate the results

Question 6

formula for moles –> # of particles

Answer 6

N = nxMa

Question 7

formula for # of particles –> moles

Answer 7

n = N/Na

Question 8

formula for mass –> moles

Answer 8

n = m/M (molar mass)

Question 9

formula for moles–> mass

Answer 9

m = nM

Question 10

what is percentage composition

Answer 10

refers to the relative mass of each element in the compound

Question 11

what law of percentage composition obey

Answer 11

law of definite proportions (where elements in chemical compounds are always present in the same proportions by mass)

Question 12

hydrate definition

Answer 12

inorganic salts containing water molecules combined in a definite ratio to their crystal structure

Question 13

water of hydration meaning

Answer 13

water that is evaporated from the crystal structure of hydrate

Question 14

anhydrous meaning

Answer 14

compound remaining once water of hydration is removed

Question 15

percentage yield meaning

Answer 15

measure of efficiency of conversion of reactants to products