(Chemistry) Unit 3B: Post Assessment

The table shows properties of several elements.

Element Melting Point (°C/K) Boiling Point (°C/K) Color

Carbon 3500/3773 4827/5100 Black

Chlorine -101/172 -35/238 Green

Hydrogen -259/14 -253/20 Colorless

Oxygen -218/55 -183/90 Colorless

Sodium 98/371 883/1156 Silvery

A student combines elements as given by the formula C₂H₄O₂.

What prediction can the student make about the new substance's properties?

• The new substance will be black and have a high melting point.

• The new substance may have different chemical and physical properties than the elements that make it up

• The new substance will be green and have a low melting point.

• The new substance will be silvery and have a high boiling point.

Directions: The table shows properties of several substances. Use the table to answer any
questions that follow.
Substance Boiling Point (°C) Soluble in Water
NaCI     1413 Yes
He          -269 No
N₂         -320 Yes
HCI         109 Yes

A sample of an unknown substance, X, is found to be gaseous at room temperature, and it dissolves in water. Which is X?

• NaCl

• He

• N₂

• HCl

Directions: The table shows properties of several substances. Use the table to answer any
questions that follow.
Substance Boiling Point (°C) Soluble in Water
NaCI     1413    Yes
He         -269      No
N₂          -320    Yes
HCI.        109      Yes

The best way to turn helium gas into liquid helium is:

• Using a compressor

• by lowering its temperature to less than -269^o C

• Applying high pressure

• Using a magnetic field

A table of the properties of various substances is shown below. Substance Name Density (g/cm3) Melting Point (in °C) Boiling Point (in °C) Methanol acetate 0.93 -98 57 Acetone 0.79 -95 57 Isopropanol 0.79 -89 82 t-Butanol 0.79 26 83 Cycloheptane 0.81 -12 118 n-Butanol 0.81 -90 118 s-Butanol 0.81 -89 100 A student is given an unknown, clear, colorless liquid at room temperature. The student measures the density, melting point, and boiling point of the liquid. What would the student conclude if he or she found out that the unknown had a density of .79 g/cm3 and a boiling point is 82.05°C?

• Methanol acetate

• Acetone

• Isopropanol

• t-Butanol

A data table of the solubility of two solids in various liquids is shown below.
Solid Substance Liquid A Liquid BLiquid C
X soluble soluble insoluble
Y insoluble soluble soluble

Which of the following can be determined from the data?

• None of the substances are the same

• All three liquids are the same

• Two of the liquids are the same

• The two solids are the same

The diagram shows the chromatogram from a thin-layer chromatography experiment involving known solutions 1, 2, 3 and 4, and an unknown solution. Use the diagram to answer any questions that follow.

Which characteristic property of the substances in the solutions does thin-layer chromatography utilize?

• Boiling point

• molecular polarity

• Density

• Refractive index

The diagram shows the set-up for an experiment to determine the composition of four different types of ink. Which process is being used in the diagram?

• filtration

• distillation

• gas chromatography

• paper chromatography

The table shows properties of several elements. Use the table to answer any questions that follow.
Element Melting Point (°C/K) Boiling Point (°C/K) Color
Carbon 3500/3773 4827/5100 Black
Chlorine -101/172 -35/238 Green
Hydrogen -259/14 -253/20 Colorless
Oxygen -218/55 -183/90 Colorless
Sodium 98/371 883/1156 Silvery

Table salt is a white solid with the chemical formula NaCl. Which of the following is true of table salt?

• Table salt is a compound of sodium and chlorine with different physical characteristics than the elements that make it up.

• Table salt is a compound of carbon and hydrogen with different chemical characteristics from the elements that make it up.

• Table salt could not have been formed by any of the elements in the table, as it has different physical characteristics.

• Table salt must have been formed by sodium and carbon, as they are the only elements that are solids at room temperature.

Four substances have properties as shown in the table below.
Substance Number Density
(in g/cm3 at STP)
Melting Point
(in °C)
Boiling Point
(in °C)
I 0.93 -98 57
II 0.79 -95 57
III 0.79 26 83
IV 1.47 26 296

Which two substances could be the same?

• I and II

• no two could be the same

• III and IV

• I and IV

What could be used to separate substances of different densities from a mixture?

• Filtration

• Evaporation

• Centrifugation

• Distillation