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lina2011 [118]
2 years ago
12

A new student is planning to use thin layer chromatography (TLC) for his research project. After setting up the apparatus the st

udent forgets to place a lid on the TLC jar. He obtains poor results after running the TLC experiment. Which of the following can best explain his bad results?
A. The open system evaporates the solvent on the TLC plate
B. The open system prevents the evaporation of the solvent in the solution
C. The open system prevents the evaporation of the solvent on the TLC plate
D. The open system evaporates the solvent in the solution
Chemistry
1 answer:
tamaranim1 [39]2 years ago
7 0

Answer:

The open system evaporates the solvent in the solution

Explanation:

An open system is a system in which exchange of materials and energy can occur. If a TLC set up is left open, then the set up constitutes an open system.

During TLC, the sample is dotted on the plate and inserted into a suitable solvent. The solvent moves up the plate and achieves the required separation of the mixture.

Most of these solvents used used TLC are volatile organic compounds. Therefore, if the TLC set up is left open, the solvent will evaporate leading to poor results after running the TLC experiment.

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Which is most likely true about electronegativity?
VikaD [51]

Electronegativity is the tendency of an element to attract the bonded electrons towards itself. In a group, as the atomic radius increases electronegativity decreases as the outermost electron is far away from the nuclear attraction. In a period, the atomic size decreases. So, the effective nuclear charge experienced by the outermost shell increases. Therefore, across a period the electronegativity increases as the increased effective nuclear charge leads to the attraction of bonded electrons with greater ease.

Therefore the correct answer is <u>c</u>, electronegativity tends to increases across a period.

8 0
2 years ago
Avanti works in a bookstore. She has four books and is going to place them in two stacks. The diagram above shows the books befo
Feliz [49]

Answer:

Well they didn't transfer any energy when they weren’t touching and it did t produce any energy if it didn’t move. Since they are on top of each other they are causing momentum on each other creating kinetic energy

Explanation:

3 0
1 year ago
A vessel contained N2, Ar, He, and Ne. The total pressure in the vessel was 987 torr. The partial pressures of nitrogen, argon,
xz_007 [3.2K]

Answer:

The partial pressure of neon in the vessel was 239 torr.

Explanation:

In all cases involving gas mixtures, the total gas pressure is related to the partial pressures, that is, the pressures of the individual gaseous components of the mixture. Put simply, the partial pressure of a gas is the pressure it exerts on a mixture of gases.

Dalton's law states that the total pressure of a mixture of gases is equal to the sum of the pressures that each gas would exert if it were alone. Then:

PT= P1 + P2 + P3 + P4…+ Pn

where n is the amount of gases present in the mixture.

In this case:

PT=PN₂ + PAr + PHe + PNe

where:

  • PT= 987 torr
  • PN₂= 44 torr
  • PAr= 486 torr
  • PHe= 218 torr
  • PNe= ?

Replacing:

987 torr= 44 torr + 486 torr + 218 torr + PNe

Solving:

987 torr= 748 torr + PNe

PNe= 987 torr - 748 torr

PNe= 239 torr

<u><em>The partial pressure of neon in the vessel was 239 torr.</em></u>

4 0
2 years ago
A 0.050 M solution of AlCl3 had an observed osmotic pressure of 3.85 atmatm at 20°C.Calculate the van't Hoff factor iii for AlCl
Alja [10]

Answer:

The actual Van't Hoff factor for AlCl3 is 3.20

Explanation:

Step 1: Data given

Molarity of AlCl3 = 0.050 M

osmotic pressure = 3.85 atm

Temperature = 20 °C

Step 2: Calculate the Van't Hoff factor

AlCl3(aq) → Al^3+(aq) + 3Cl^-(aq)

The theoretical value is 4 ( because 1 Al^3+ ion + 3 Cl- ions) BUT due to the interionic atractions the actual value will be less

Osmotic pressure depends on the molar concentration of the solute but not on its identity., and is calculated by:

π = i.M.R.T

 ⇒ with π = the osmotic pressure = 3.85 atm

⇒ with i = the van't Hoff factor

⇒ with M = the molar concentration of the solution = 0.050 M

⇒ with R = the gas constant = 0.08206 L*atm/K*mol

⇒ with T = the temperature = 20 °C = 293.15 Kelvin

i = π /(M*R*T )

i = (3.85) / (0.050*0.08206*293.15)

i = 3.20

The actual Van't Hoff factor is 3.20

6 0
2 years ago
An irregularly shaped solid which has a mass of 10.283g was placed in a graduated cylinder containing an inert liquid. The initi
Gwar [14]
Liquid  + Solid = 8.89 mL
V ( Solid ) = 8.89 mL - 6.26 mL = 2.63 mL
The density of the solid = m / V = 10.283 g / 2.63 mL =
= 3.9 g/mL = 3.9 g / cm³
3 0
2 years ago
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