CHEM 109
Introduction to Chemistry
Fall 2015
Name:
Examination 1
Multiple Choice Questions
1.
Which of the following is a physical process?
a)
b)
c)
d)
2.
Which of the following is a chemical property of a substance?
a)
b)
c)
d)
3.
Solubility of Sodium Chloride in Water = 35 g/100mL.
Melting Point of Water = 0oC
Cadmiun metal dissolves in Nitric Acid, producing a Blue tinted solution. *****
Density of Hexane =0.67 g/mL.
Which of the following is an extensive physical property of matter?
a)
b)
c)
d)
4.
An antique silver spoon has tarnished significantly.(Silver is chemically reacting with Air)
Sand is filtered from Sea Water.*****
Metallic Sodium dulls when exposed to Air.(Sodium is chemically reacting with Air)
A pot roast is cooked in an oven.(Involves a number of different chemical reactions)
length
*****Double the size, double the length
melting point
color
freezing point
The intensive physical properties of a substance are important because they:
a) allow us to determine how much of the substance is required in a chemical reaction.
b) help us identify or characterize the substance. *****
c) provide information about the atomic structure of the substance.
5.
What type of error will “wetting” by the expansion liquid in a stem thermometer along the
stem’s bore give rise to?
a) Systematic *****Causes the liquid column to rise too high; unidirectional and
b) Random
assignable cause.
c) Gross
6.
Which of the following types of errors can be traced to an defect in the measuring
instrument?
a) Systematic *****
b) Random
c) Gross
7.
Systematic errors lead to a lack of:
a)
b)
b)
c)
8.
accuracy in the measurement. *****
significant digits in the measurement.
precision in the measurement.
gradation of the measuring instrument.
How many significant figures does the following measurement contain?
temperature = 0.0023oC
a)
b)
c)
d)
9.
2
3
4
∞
*****Three zeros to the left are place holders and therefore are not significant
How many significan figures does the following measurement contain?
3 coins
a)
b)
c)
d)
10.
1
2
3
∞
*****There is no uncertainty in the number
What is the result of the following calculation, reported to the correct number of significant
figures?
0.12g + 0.003g = ?
a)
b)
c)
d)
0.123g
0.12g *****
0.1g
0.g
0.12
0.003
0.123
0.12
(least precise measurement)
(more precise measurement)
(after eliminating non-significant digit)
11.
How many significant figures does the result of the following calculation contain?
1.554oC - 0.47oC
a)
b)
c)
d)
12.
1
2
3
4
*****
1.554
0.47
1.084
1.08
(more precise measurement)
(least precise measurement)
(after removing the non-significant digit)
(3 sig figs)
What is the result of the following calculation, reported to the correct number of significant
figures.
2.518 g / 1.2 mL
a)
b)
c)
d)
2.098 g/mL
2.10 g/mL
2.1 g/mL *****
2. g/mL
2.518 (4 sig figs)
1.2
(2 sig figs)
= 2.1 (2 sig figs)
13.
What is the following number in standard decimal notation?
0.241 x 103
a)
b)
c)
d)
14.
0.000241
0.0241
241. *****
24100.
Which of the following represents the most precise measurement of length?
a)
b)
c)
d)
3.1 x 10-1
4.766 x 10+2
1.6 x 10-3
*****
8.20 x 10+3
=
=
=
=
0.31
476.6
0.0016
8200.
15.
How many significant figures should be reported for the result of the following calculation?
(3.110 x 10-3) x (0.021 x 10+2)
a)
b)
c)
d)
16.
1
2
3
4
***** (3.110 x 10-3) x (0.021 x 10+2) = (6.5 x 10-3)
4 sig figs
2 sig figs
2 sig figs
What is the result of the following calculation to the correct number of significant figures?
(2.14 x 104) - (1.11 x 102)
a)
b)
c)
d)
17.
2.14 x 104
0.01111 x 104
2.1511 x 104
(least precise measurement)
(more precise measurement)
The SI Unit standard for mass is the:
a)
b)
c)
d)
18.
2.1511 x 104
2.151 x 104
2.15 x 104 *****
2.1 x 104
Pound (lb)
gram (g)
slug (sl)
kilogram (kg) *****
What quantity is measured using the following unit?
cubit2
a)
b)
c)
d)
length
volume
area ******
mass
length x length
Short Answer Questions
1.
Most precise volume measuring devices have markings along a narrow neck? Why do you
think this is important?
Small volume additions to the narrow-necked device will give a greater
height change than for the wider device.
2.
Identify one substance in this room and indicate one physical and one chemical property of
that substance.
Open Ended
Example:
3.
Piece of Paper
Physical Property: color is White
Chemical Property: combusts in Air
Distinguish between Systematic and Random errors. Give an example of each type of
error.
Systematic Error:
is unidirectional and due to an assignable cause;
degrades accuracy.
Ex: Ruler smashed at one end.
Random Error:
gives fluctuating measurements and no assignable
cause; degrades precision
Ex: Balance on a wobbly table.
4.
Suppose a determination of the diameter of Carbon atom yields a result of 9.1 x 10-9 cm.
The currently accepted value for this diameter is 1.54 x 10-8 cm. What is the percentage
error in the determination?
% error =
= 41%
5.
What is the difference between an instrument's resolution and the precision with which it
can be used?
Resolution is the ability of the device to distinguish two measurements. It
only involves the construction of the instrument.
Precision is a measure of how repeatable a measurement is; and, depends on
both the construction of the instrument and the ability of the user to reliably
use the instrument.
6.
Why might we use significant digits in one situation to report the precision of a
measurement and use the standard deviation in another?
Sigs-figs are quick and dirty, but crude. To be correct, we should take
multiple measurements and determine the standard deviation of the mean.
This will generally give us a better/quantitative estimate of the precision.
And,
this generally takes more time……
7.
Report the following result to the correct number of significant figures:
3.221 - ((4.33 x 10-6) / (2.7 x 10-5))
4.33 x 10-6
2.7 x 10-5
(3 sig figs)
(2 sig figs)
= 1.604 x 10-1 = 0.16
3.221
0.16
3.061
3.06
(2 sig figs)
(more precise)
(least precise)
(after removing the non-significant digit)
8.
A 25.09g cube of Cadmium metal, an element which forms some of the most toxic salts
known, has its volume measured with a ruler, as pictured below:
a) What is the length of one side of the cube, reported to the correct number of significant
digits?
length = 1.45 cm
(Must be to the 1/100 ths place for the sig figs.
Must have units specified.)
b) What is the volume of Cadmium metal; reported to the correct number of significant
digits?
volume = (1.45 cm)3 = 3.05 cm3
(Must have three sig figs and a volume unit.)