ANACHEM Flashcards
A step in the analytical process that involves transforming the sample into something that is appropriate for the analysis.
Sample Preparation
You are given a cube of pure copper. You measure its density three times and the values recorded are 7.97 g/cm, 9.01 g/cm, 9.36 g/cm. Copper’s accepted density is 8.96 g/cm. What is your percent error?
2%
(9.23±0.03 + 4.21±0.02)-3.26±0.06
Compute for the absolute certainty and % relative uncertainty.
10.18±0.07; 0.7%
Process being used to obtain salt from ocean water?
evaporation
What is 78,590 rounded to two significant figures?
79000
Process that is commonly used to separate colored substances from each other?
Chromatography
An apparatus in the laboratory that is primarily used to guard against spillage when pouring chemicals from one container to another.
delivery funnel
Dylan is shooting dart pins at a target. Which of the following demonstrates high accuracy but low precision?
Dylan consistently hits around the target but never hits the bullseye
Maya buys several boxes of test tubes. On the package, it says that each box has 50 test tubes. She opens the boxes and only one of them has 50 test tubes inside, the other boxes either have too many or too few. How would you describe the box of test tube with 50 test tubes inside?
Accurate and precise.
Method of separation being utilized for mixture of iron and sulfur
magnetism
It is prepared by weighing out an appropriate portion of a pure solid and dissolving it to a measure volume of liquid.
stock solution
An experiment calls for measuring 30ml of NaCl solution in a graduated cylinder. How should the graduated cylinder be read?
Hunch down until your head is on the same level as the table top, then look to make sure the bottom of the meniscus is at 30ml
How close a measurement is to the true value is
Accuracy
True or False
Chromatography is used to identify the nature of the components of a given sample
True
Simplify: 3.85 x 10^18 /7.35 x 10^36
5.24 x10^17
Good work practices in the laboratory include
confining long hair and loose clothing
Why is volumetric flask considered as more precise in measuring volume instead of a beaker, Erlenmeyer flask etc.?
it only measures specific volume of liquid
Simplify: 26.14/37.62 x 10^8(4.38 x 10^2)
3.04 x 10^10
Simplify: 9.24-1.342/2.3
3.43
Simplify: a^9b^14/(ab)^7
a^2b^7
Which of the following is TRUE about the volume of solvent and moles of solute in a diluted solution?
The increase in volume makes the solution unsaturated while the moles of solute remain constant.
Water can be separated from alcohol by simple distillation because
They have different boiling points
Compute the absolute and % relative uncertainty for the given and express the answer to the correct number of significant digits.
(91.3±1.0) (40.3±0.2)/ 21.2 ±0.943
174± 3; ±2%
Which list shows the numbers in order from least to greatest?
3.8 x 10^-3, 8.3 x 10^-3, 3.8x 10^-2
Analysis that involves description and illustrations that cannot be measured is
Qualitative
Which of the following could prevent systematic error?
periodic calibration of instruments
There are () significant digits in the number 80,000.00
7
True or False
The following should be done when measuring a mass of a substance: always make sure that the draft shield/cover is properly closed when measuring the mass.
False
You are trying to synthesize and important organic compound in the lab and you need exactly 9ml of chloroform for the next reaction. Which measuring tool would be the most accurate to measure that liquid?
10ml graduated cylinder
In filtration, what name is used to describe the solid left in the filter paper?
residue
Simplify. (5.64x10^-7) (6.1x10^4). Write your answer in scientific notation
3.4x10^-2
Write (x) (x) (x) (x) (x) in exponential form?
X^5
The pipette is 8.7 long
7 is the estimated digit
Part of the analytical balance that allows the user to reset the weight on the scale.
TARE button
A student adds 6.00g of a solid to 30.0mL of water. The solid has a molar mass of 72.0g/mol. What is the molar concentration of the solution? (If necessary to the calculation, assume that 1.00g of the solid has a volume of 1mL)
2.78mol/L
Field of chemistry that deals with instrumentation and quantifying matter.
Analytical Chemistry
Which of the following pipettes has a graduation that ends before the tip?
Mohr
Method of chemical analysis that deals more with weighing the mass of chemicals substances.
gravimetric
Forgetting to TARE a balance is an example of
Personal Error
Repeated measurements of a quantity can reduce the effects of
random errors
When heating a liquid or solution in a test tube over an open flame:
Heat it gently and point it away from anyone nearby
True or False
If a measurement result has uncertainty then it means that the measurement was not performed correctly.
True
Method of separation that is used for substances that are immiscible like oil and water.
Extraction
Write the number 8.56 x 10^3 in standard form
0.00856
A set of data are all close to each other, but are not close to the actual value is
precise
Wet method is a qualitative analysis that makes use of a solvent to dissolve the sample before analyzing it. Which of the following are examples of wet methods?
Both gravimetric and volumetric are wet methods
You weigh a substance on a balance and it measures 23.49. The estimated digit is
9
Why is ‘weighing by difference’ accurate than direct weighing?
it eliminates systematic errors
The following are placed in a beaker weighing 41.568g: 3.798g of NaCl, 2.36g of sand and 6.0g water. What is the final mass of the beaker?
53.73g
The part of the mixture that passes through the filter paper is the
filtrate
Find the absolute and percent relative uncertainty and express your answer to the correct number of digits.
(3.4±0.2 x 10^-8) ÷ (2.6± 0.1 x 10^-3)
1.3 ± 0.09x 10^-11; ±7%
If the beaker containing a sample of alcohol weighs 50.9878g and the empty beaker weighs 49.325g, what is the weight of the alcohol?
1.663g
Write the number 0.964 in scientific notation.
9.64 x 10^-1
Which of the following is best used for storing and mixing liquids?
beaker
A blow out pipette
measures the volume of the last remaining drop of liquid.
A graduated cylinder upon measuring the same sample three times gave 566mL, 584mL, and 541mL. The average of these three values is 563.7mL. If the true value was 563.688mL, how would you explain the accuracy and precision of the measurements?
The average value is accurate but the individual values are neither accurate nor precise.
True or False
sources of heat inside the laboratory: Fire Blanket
False
You need to prepare 250.0mL of a 2.50M HCl solution using the stock solution 12.0M HCl. What volume of 12.0M HCl is required for this dilution?
52.1mL
Which of the following is the confirmatory test for the presence copper ions?
Addition of HNO to dissolve the Cu^2+ precipitate then, continuously add NH3