SCHOOL OF CHEMISTRY
CHEM 181 – ADDITIONAL EXERCISE 1 - 2011
1.
CLASSIFICATION AND PROPERTIES OF MATTER
(a).
Define the following terms:
(i)
(b).
(iii)
a mixture
a physical property and a chemical property
Oxygen gas supports combustion
Fertilisers help to increase agricultural production.
Water boils below 100oC on top of a mountain.
Lead is denser than aluminium.
Uranium is a radioactive substance.
Which of the following properties are intensive and which are extensive?
Give their SI units.
(i)
(ii)
(iii)
(iv)
(e).
a substance
Do the following statements describe chemical or physical properties?
(i)
(ii)
(iii)
(iv)
(v)
(d).
(ii)
Explain the difference between:
(i)
(c).
matter
length
volume
temperature
mass
Indicate which of the following materials is a pure substance, a homogeneous
mixture, or a heterogeneous mixture?
(i). air from the city of Durban
(ii). paint
(iii). perfume
(iv). carbon monoxide
(v). sea water
(vi). one carat diamond
(vii). A bottle of wine
(viii). A 2.5 L of 30 % hydrogen peroxide
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2.
DENSITY
(a)
Calculate the density of mercury if 1.00  102 g occupies a volume of
7.36 cm3.
(b)
Calculate the volume of 65.0 g of the liquid methanol (wood alcohol) if its
density is 0.791 g/mL.
(c)
What is the mass in grams of a cube of gold (density = 19.32 g/cm3) if the
length of the cube is 2.00 cm?
(d).
Calculate the density of a 374.5-g sample of copper if it has a volume of
41.8 cm3.
(e)
A student needs 15.0 g of ethanol for an experiment. If the density of ethanol
is 0.789 gmL, how many milliliters of ethanol are needed?
(f)
What is the mass, in grams, of 25.0 mL of mercury (density = 13.6 g/mL)?
3.
METRIC SYSTEM
(a)
What is the name given to the unit that equals:
(i) 10–9 gram, (ii) 10–6 second, (iii) 10–3 meter?
(b)
What decimal fraction of a second is a picosecond, ps?
(c)
Express the measurement 6.0  103 m using a prefix to replace the power of
ten.
(d)
Use exponential notation to express 3.76 mg in grams.
(e)
A unit of energy used in atomic spectroscopy is the wavenumber. This has
the units of reciprocal centimeters, cm-1 i.e. it is the number of waves per
centimeter.
Convert 1000 cm-1 to m-1.
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4.
TEMPERATURE SCALES
(a)
Convert the following temperatures to degrees celcius, kelvin or
Fahrenheit
(i)
(ii)
(iii)
(iv)
(v)
(vi)
(vii)
(viii)
95oF, the temp on a hot summer day
12 oF the temp on a cold winter day
102 oF fever
-273 oC (theoretically the lowest attainable temp)
-183 oC boiling point of oxygen
77K, boiling point of liquid nitrogen
4.2K, boiling point of helium
601K, melting point of lead
(b)
Convert the following temperatures to Kelvin (K):
(i)
(ii)
(iii)
(iv)
(v)
113 oC , melting point of sulfur
37 oC, normal body temp
357 oC , boiling point of mercury
451oF, ignition temp of paper
32oF
(c).
Ethylene glycol, the major ingredient in antifreeze, freezes at −11.5ºC.
What is the freezing point in (a) K, (b) °F?
5.
SIGNIFICANT FIGURES
(a)
How many significant figures are in each of the following numbers (assume
that each number is a measured quantity):
(i) 4.003, (ii) 6.023  1023, (iii) 5000 (iv) 4867 mi (v) 60.104 ton
(vi) 40.2 g cm-3 (vii). 0.0000003 cm (viii). 4.6 x 1019 atoms
(b)
Express the following numbers in scientific notation:
(i). 0.000000027 (ii). 35678 (iii). 47764 (iv). 0.096
(c)
Express the following as decimals:
(i) 1.5 x 10-3 (ii) 1.0 X 10-7 (iii) 1.0 X 10-1
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(d)
Carry out the following arithmetic operations to the correct number of
significant figures:
(i). 11 254.1 g + 0.1983 g (ii). 66.59 L – 3.113 L (iii). 8.16 m x 5.1355
(iv) 0.00154 kg / 88.3 mL (v). 2.64 x 10 cm3 + 3.27 cm x 102 cm
(e)
Round the following numbers to 4 significant figures:
(i) 10.6451 (ii) 10.6450 (iii) 10.6449 (iv) 0.64555 (v) 0.64554
(f)
The width, length, and height of a small box are 15.5 cm, 27.3 cm, and 5.4 cm,
respectively. Calculate the volume of the box, using the correct number of
significant figures in your answer.
#(g)
A gas at 25°C fills a container whose volume is 1.05  103 cm3. The container
plus gas have a mass of 837.6 g. The container, when emptied of all gas, has a
mass of 836.2 g. What is the density of the gas at 25°C using the correct
number of significant figures in your answer?
(h)
To how many significant figures should the mass of the container be
measured (with and without the gas) in question (g) in order for the density
to be calculated to three significant figures?
(i)
It takes 10.5 s for a sprinter to run 100.00 m. Calculate the average speed of
the sprinter in meters per second, and express the result to the correct
number of significant figures.
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