ANACHEM - PRELIM Flashcards by Karyle Lacanaria

A step in the analytical process that involves
transforming the sample into something that
is appropriate for the analysis.

Sample Preparation

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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?

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(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%

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Process being used to obtain salt from ocean
water?

evaporation

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What is 78,590 rounded to two significant
figures?

79000

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Process that is commonly used to separate
colored substances from each other?

Chromatography

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An apparatus in the laboratory that is
primarily used to guard against spillage
when pouring chemicals from one container
to another.

delivery funnel

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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

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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

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Method of separation being utilized for
mixture of iron and sulfur

magnetism

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It is prepared by weighing out an appropriate
portion of a pure solid and dissolving it to a
measure volume of liquid.

stock solution

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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

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How close a measurement is to the true
value is

Accuracy

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Which of the following is TRUE about
chromatography?

It is use to identify the nature of the
components of a given sample.

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Simplify: 3.85 x 10^18 /7.35 x 10^36

5.24 x10^17

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Good work practices in the laboratory
include

confining long hair and loose clothing

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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.

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Simplify: 26.14/37.62 x 10^8(4.38 x 10^2)

3.04 x 10^10

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Simplify: 9.24-1.342/2.3

3.43

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Simplify: a^9b^14/(ab)^7

a^2b^7

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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.

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Water can be separated from alcohol by
simple distillation because

They have different boiling points

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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%

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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

The following should be done when measuring a mass of a substance EXCEPT:

always make sure that the draft shield/cover is properly closed when measuring the mass.

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

500 cc

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

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

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

The following are the other sources of heat inside the laboratory EXCEPT:

fire blanket

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