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
In titration, the solution of known concentration is the
A. standard solution
B. titrant
C. Both
C
The phosphorus in a sample of phosphorus rock weighing 0.5428g is precipitated as MgNH4PO4.6H2O and ignited to Mg2P2O7 If the ignited precipitate weighs 0.2234g.
Calculate the % of P2O5 in the sample
-26.25
The weight of MgNH4PO4.6H2O
-0.4927
A substance that dissolves in water and conducts electricity when present in an aqueous solution is
Ionic
Process that allows coagulated particles to revert to disperse state is known as
Peptization
Which of the following cations is considered most toxic heavy metal that could affect the nervous system?
Mercury ion
A weak acid, HF, is in solution with dissolved sodium fluoride, NaF to make buffer solution. If HCl is added, which ion will react with the extra hydrogen ions from the HCl to keep the pH from changing?
OH-
A solution was known to contain both Ag+ ions and Bi3+ ions. Which of the following could be added to separate them in such a way that one ion would end up in a precipitate, while the other remained in solution?
HNO3
If 8.19g KIO3 is dissolved in enough water to make 500.0mL of solution, what is the molarity of the potassium iodate solution? The molar mass of KIO3 is 214g/mol.
7.65 x 10^-2 M
A process in which equations are arranged so that unwanted units cancel and only the desired units will remain.
Dimensional analysis
The equation below shows the decomposition of lead nitrate. How many grams of oxygen gas are produced when
11.5 g NO is formed? (N -14 g/mol; O-16 g/mol)
2Pb(NO3)2(s) –> 2PbO(s) + 4NO2(g)+ O2(g)
1.00g
Dispersed particles in liquid phase, that settles spontaneously.
Colloidal suspension
The compound P4S3 is used in matches. It reacts with oxygen to produce P4O10 and SO2. The unbalanced chemical equation is shown below.
P4S3(s) + O2(g) → P4O10(s) + SO2(g)
What mass of SO2 is produced from the combustion of 0.331 g P4S3?
0.289 g
An electrolyte that partially dissociates in water
Weak Electrolyte
True or False
In titrimetric analyses, secondary standards are usually standardized against a primary standard.
False
True or False
The following are colligative properties: gas solubility as a function of partial pressure above a solution (Henry’s law)
False
Which of the following compounds is the deep blue color complex of copper ion?
Cu(NH3)(^2+)4
Le Châtelier’s Principle states that if a chemical system at equilibrium is stressed,
the system will adjust to reduce the stress.
True or False
Sodium Hydroxide a common titrant in titration of bases is also considered as a primary standard.
False
A solution is prepared by dissolving 4.40g of KSCN in enough water to make 340mL of solution. What is the concentration of the solution?
0.133 M
A Bronsted-Lowry base is defined as
a proton acceptor
Which of these compounds is most likely to be covalent?
CS2
A 1.45 g sample of chromium contains () atoms.
1.68 x 10^22
If 16.4 g of oxygen gas react with excess hydrogen, what mass of water is produced? 2H2(g) + O2(g) →2H2O(g)
18.5 g
Which of these compounds is most likely to be ionic
ICl
Which of the following is the correct Kb expression for HPO4(^2-) if added to water?
Kb = [H2PO4-][OH-]/[HPO4(^2-)]
What is the mass percent of each element in sulfuric acid, H2SO4?
2.055% H, 32.69% S, 65.25% O
True or False
Osmosis involves the movement of a solvent through a semipermeable membrane
True
True or False
Osmotic pressure is a colligative property.
True
The molar mass of boron is 10.81 g/mole. What is the mass of a single boron atom?
6.510 x 10^24g
What concentration unit is necessary for the calculation of vapor pressure lowering?
mole fraction
Which of the following is the strongest acid?
Oxalic Acid Ka = 5.9 × 10^-2
If a solution is prepared by dissolving 7.7g of lithium iodide, LiI, in enough water to make 400mL of solution, what is the %(w/v) of LiI?
1.9%
What volume of 6.0M HNO3 is required to prepare 250mL of 0.40M HNO3?
17mL
A 0.6025g sample of a chloride salt was dissolved in H2O and the chloride precipitated by adding excess silver nitrate. The precipitate of silver chloride was filtered, washed, dried and found to weigh 0.7134g. Calculate the % Cl in the sample.
29.29%
How many liters of 0.2805 M C4H12O6(aq) contain 1.000g of C6H12O6 ?
0.01979 L
Name the basic parts of a titration set-up
Name of basic part 1- Burette clamp Name of basic part 2- Burette
Name of basic part 3- Iron ring
Name of basic part 4- Erlenmeyer flask Name of basic part 5- Analyte
The curve upper surface of liquid in a burette or graduated cylinder is the
meniscus
Given the following equilibrium, which of the following statements is TRUE if additional F is added to the solution? HF(aq)+ H2O (l) –> H3O+(aq) + F-(aq)
[H3O+] will decrease and the pH value will increase
A temperature dependent concentration that is often used to measure the colligative properties of substances
m
True or False
It’s a “dynamic equilibrium”: reactants and products are constantly changing
False
What is the mass percent of each element in sulfuric acid, H2SO4?
2.055% H, 32.69% S, 65.25% O
A 0.1298g sample of pure acid was titrated with 42.11ml of 0.1234 N NaOH. What is the equivalent weight of the acid?
24.98
Given the reaction at equilibrium: N2(g)+ 3H2(g) <–> 2NH3(g) . If the pressure is increased at constant temperature, there will be an increase in the number of moles of
NH3 only
Which of the following liquids will be miscible with water in any proportions: ethanol (CH3CH2OH), carbon tetrachloride (CCl4), hexane (C6H14), and/or formic acid (HCO2H)?
ethanol and formic acid
Which of the following is a substance that ionizes completely in a solution?
a strong electrolyte
Which of the following is NOT part of Group II cations?
Cobalt
When computing for the equivalent weight, what are the values that you will consider?
-the weight in grams
-molar mass
How many hydrogen atoms are present in 1.0g of NH3?
3.5 x 10^22 atoms
Which of the following is the confirmatory reagent for bismuth ion?
Na2SnO2
Crystalline NaF is added to a dilute solution of hydrofluoric acid (HF). What happens to the hydrogen ion concentration as a result of this addition?
Unchanged
Ammonia reacts with diatomic oxygen to form nitric oxide and water vapor:
4NH3 + 5O2 → 4NO + 6H2O
When 20.0g NH and 50.0g O are allowed to react, which is the limiting reagent?
NH3
What is the [H+] concentration of a solution with pH = 3.48?
3.31 x 10^-4M
What is the weight of NaCl in a 0.500L bottle of 2.00M NaCl?
58.4g
Which of the following is used to increase the rate of sedimentation for cation analysis?
Centrifuge
What concentration unit is necessary for the calculation of boiling point elevation?
molality
The moles of solute per liter of solution is expressed by
M
Unknown X was treated with six drops of HCl. A precipitate was observed. Which of the following ions could be present?
Tin ion
How many moles of HCl are present in
0.098 grams of HCl?
0.0027 mol
A pipette that can measure and transfer various amounts of liquid is
serological
A molecule is found to contain 47.35% by mass C, 10.60% by mass H, and 42.05% by mass O. What is the empirical formula for this molecule?
C3H8O2
A solution is prepared by 100mL of 10M HCl to 1L volumetric flask and filling it to the mark with water. What is the pH of the solution?
1
Which of the following is the product of the reaction between a solution containing soluble ion of silver and nitric acid?
[Ag(NH3)2]Cl
Which is a correct method for calculating the moles of calcium carbonate present in 132 grams of calcium carbonate?
132gCaCO3 (1mol/100.1g)
An aqueous solution containing a concentration of 2.5 X 10 OH ions will have a pH of which of the following?
6.40
A solution of anything in water is known as
aqueous
Which laboratory equipment is needed to prepare solutions of known %(w/w)?
a volumetric flask
In a solution of a solid in a liquid, the solid is called which of the following?
Dissolve
Given the Ka values shown, which one of the anions shown is the weakest base?
CH COOH (Ka = 1.8 x 10^-5)
HCOOH (Ka = 1.0 x 10^-4)
HClO (Ka = 3.0 x 10^-8)
HF (Ka = 6.8 x 10^-4)
F-
When alcohol is dissolved in water which would normally be the solute?
the compound present in smaller amount
The pH of a 1.25 x 10-3 M NaOH solution is:
3.10
What is the mass of 0.71 mol Na?
16g
In a solution of a solid in a liquid, the liquid is called which of the following?
dissolver
A 0.001 M aqueous solution of HCl has a pH of
3.0
A substance that changes in color at equivalence point.
indicator
An iron ore was analyzed by dissolving a 1.1324g sample in concentrated HCl. The resulting solution was diluted with water and the iron (III) was precipitated as hydrous oxide Fe2O3.xH2O by the addition of NH3 After filtration and washing, the residue was ignited at a high temperature to give 0.5394g of pure Fe2O3 (FW= 159.69).
Calculate the % Fe O (FW= 231.54) in the sample?
Calculate the % Fe (55.847)
46.04; 33.32
How many grams are in 1.946 moles of NaCl? (Na - 23 g/mol; Cl - 35 g/mol)
112.9g
True or False
The TARE button in the analytical balance cancels the weight of the container
True
Method of analysis that involves measurement of the mass of the product to calculate the quantity of the original analyte.
Gravimetric Analysis
A 0.45 M solution of a newly discovered weak acid HZ has a pH of 2.60. What is the value of Ka for HZ?
HZ + H2O <—> H3O+ + Z-
1.4 x 10-5 M
Which of the following is the supernatant liquid from precipitating insoluble chlorides?
HCl
For the following system at equilibrium, what will cause the shift toward left side of the reaction?
UO2(s) + 4 HF(g) <-> UF4(g) + 2 H2O(g
adding UF4(g)
If 25.00mL of 2.00M NaCl is transferred by pipet into a volumetric flask and diluted to 5.00L, what is the molarity of the diluted NaCl?
0.0100M
Which is a correct method for determining the mass in grams of 0.190mol silver?
0.190mol Ag(107.9g/mol)
Particles that are invisible to the naked eye.
colloidal suspension
To prepare 0.250L of 0.100M aqueous NaCl (58.4 g/mol), one may
dissolve 1.46g of NaCl in enough water to make 0.250L of solution
Which of the following compounds shows an orange precipitate for a confirmatory test?
Sb2S3
In which reaction will the point of equilibrium shift to the left when the pressure on the system is increased?
CaCO3(s) <-> CaO(s) + CO2(g)
A 0.25 M solution of carbonic acid has a pH of 3.48. What is the Ka of the solution?
H2CO3 + H2O <-> HCO3- + H3O+
4.4 x 10^-7
What is the solubility product expression for Fe2(CO3)3?
Ksp = [Fe2+]^2[CO3^2-]^3
