measurement

Question 1

uncertainty

def, calculation

Answer 1

= the doubt about the result of any measurement and its quantification
= (smallest division of measurement)/2

Question 2

error

def, types

Answer 2

= the difference between the measured and true value of the thing being measured
systematic, random

Question 3

systematic error

Answer 3

⇒ caused by instrumentation errors, methodology errors and personal errors
always either greater or lesser than the true value

Question 4

random error

Answer 4

• ⇒ occur randomly and affect measurements in an unpredictable manner
• due to carelessness, lack of concentration, uncontrolled variables
• reduce the risk with repeating the measurements several times
• can be greater or lesser than the true value

Question 5

percentage error

Answer 5

= (|literature value - experimental value|) : literature value = random error + systematic error

Question 6

precision vs accuracy

Answer 6

precision ⇒ how close the measurements are to each other (affected by random error)
accuracy ⇒ how close a measurement is to the true value (affected by systematic error)

Question 7

addition and subtraction with uncertainties

Answer 7

add uncertainties (ΔX)

Question 8

multiplication and division with uncertainties

Answer 8

add relative uncertainties (δx = ΔX/X)

Question 9

scientific notation

Answer 9

only positive numbers
1 < a < 10 × 10^y

Question 10

rules for determining significant figures

Answer 10

• non-zero digits are always significant
• any zeros between two significant digits are significant
• a final zero or trailing zeros in the decimal portion are significant

Question 11

addition and subtraction with significant figures

Answer 11

round the answer to the least number of decimal places of any number

Question 12

multiplication and division with significant figures

Answer 12

least number of significant figures in any number of the problem determines the number of significant figures in the answer

Question 13

interpolation vs extrapolation

Answer 13

interpolation ⇒ estimation of unknown values within the range of known data points (more reliable)
extrapolation ⇒ estimation of unknown values outside the range of known data points (less reliable)

Question 14

reaction yield

Answer 14

• %yield = (experimental yield)/(theoretical yield)
• experimental yield ⇒ real amount of product (what we measure)
• theoretical yield ⇒ expected amount of product (what we calculate)

Question 15

callibration curve

what it is, how it is created

Answer 15

• used to determine the concentration of an unknown sample
• the curve is created from the instrumental response to a set of standard samples at a range of concentrations ⇒ data is fit with a function to enable the prediction of unknown concentrations

Question 16

R^2 factor

Answer 16

statistical measure that determines the proportion of variance in the dependent variable that can be explained by the independent variable (how well data fits the regression model, how well the model describes observed data)