Chem 280 Midterm Exam Latest 2024 WCU@ Question
and Answers
Define Chemistry: - ANSWER: Science that tries to understand how matter behaves
by studying how atoms / molecules behave
Scientific Method / steps - ANSWER: A way of learning that emphasizes
observation/experimentation to understand the world.
1. observation
2. form hypothesis
3. test hypothesis by experiment
4. form law/theory
Observations - ANSWER: measurement of some aspect of nature
- some simple w/ naked eye, others rely on sensitive instrumentation
- occasionally observation happens by chance
- usually involves measurement/description of some aspect of physical world
Hypothesis - ANSWER: tentative interpretation or explanation of observation
-good hypothesis is falsifiable -> further testing has potential to prove it wrong
Experiment - ANSWER: highly controlled observations designed to validate or
invalidate hypothesis
- these results may confirm or show hypothesis to be wrong
- hypothesis may have to be modified or discarded/replaced
- leads to scientific law
Scientific Law - ANSWER: Brief statement that summarizes past observations and
predicts future ones
The Law of Conservation of Mass. - ANSWER: All matter in chemical reaction is
neither created nor destroyed
Theory - ANSWER: one or more well-established hypothesis may for basis for
scientific theory
- theories provide broader/deeper explanation for observations + laws.
- they model nature + predict behavior that extends well beyond observations/laws
on which they are founded
- atomic theory: all matter composed of small, indestructible particles = atoms
What is the correct multiplier for the prefix centi? - ANSWER: 10-2
What is the correct scientific notation and total number of sig figs for 0.00032400? -
ANSWER: 3.2x10-4
The correct number of sig figs in the number 6.0220 is? - ANSWER: 5
, Determine the answer to the following mixed operations problem: (9.658 x 0.54) +
88.6 = - ANSWER: 93.8
Determine the answer to the following mixed operations problem: (5.321 x 0.15) +
26.1 = - ANSWER: 26.9
Determine the answer to the following mixed operations problem: (7.5 x 102 - 2.53 x
102) ÷ 8.87 = - ANSWER: 56
A silver bullet has a mass of 31.1 g and a density of 10.5 g/mL. What is the volume of
the bullet? - ANSWER: V=m/d
2.96mL
A metal object has a mass of 8.37 g. When it was placed in a graduated cylinder
containing 20.0 mL of water, the water level rose to 23.1 mL. What is the density of
the metal object? - ANSWER: d=m/v
2.7g/mL
Fahrenheit to Kelvin - ANSWER: Need celsius first
*C = *F - 32
-----------
1.8
then
*C + 273.15 = K
Define specific heat capacity and review the trends in specific heat capacity values. -
ANSWER: Specific heat capacity of a substance is the quantity of heat in joules
required to change 1g of the substance by 1*C
A copper medallion with a mass of 72.6 g initially at 21.5 °C was heated with 684 J of
heat. What is the final temperature of the copper medallion? - ANSWER: need the
SHC of copper = 0.385 J/g*C
then remember the formula:
q=m*C* delta T
Delta T = Tf-Ti
SO
Tf=Delta T + Ti
answer: 46.0*C
and Answers
Define Chemistry: - ANSWER: Science that tries to understand how matter behaves
by studying how atoms / molecules behave
Scientific Method / steps - ANSWER: A way of learning that emphasizes
observation/experimentation to understand the world.
1. observation
2. form hypothesis
3. test hypothesis by experiment
4. form law/theory
Observations - ANSWER: measurement of some aspect of nature
- some simple w/ naked eye, others rely on sensitive instrumentation
- occasionally observation happens by chance
- usually involves measurement/description of some aspect of physical world
Hypothesis - ANSWER: tentative interpretation or explanation of observation
-good hypothesis is falsifiable -> further testing has potential to prove it wrong
Experiment - ANSWER: highly controlled observations designed to validate or
invalidate hypothesis
- these results may confirm or show hypothesis to be wrong
- hypothesis may have to be modified or discarded/replaced
- leads to scientific law
Scientific Law - ANSWER: Brief statement that summarizes past observations and
predicts future ones
The Law of Conservation of Mass. - ANSWER: All matter in chemical reaction is
neither created nor destroyed
Theory - ANSWER: one or more well-established hypothesis may for basis for
scientific theory
- theories provide broader/deeper explanation for observations + laws.
- they model nature + predict behavior that extends well beyond observations/laws
on which they are founded
- atomic theory: all matter composed of small, indestructible particles = atoms
What is the correct multiplier for the prefix centi? - ANSWER: 10-2
What is the correct scientific notation and total number of sig figs for 0.00032400? -
ANSWER: 3.2x10-4
The correct number of sig figs in the number 6.0220 is? - ANSWER: 5
, Determine the answer to the following mixed operations problem: (9.658 x 0.54) +
88.6 = - ANSWER: 93.8
Determine the answer to the following mixed operations problem: (5.321 x 0.15) +
26.1 = - ANSWER: 26.9
Determine the answer to the following mixed operations problem: (7.5 x 102 - 2.53 x
102) ÷ 8.87 = - ANSWER: 56
A silver bullet has a mass of 31.1 g and a density of 10.5 g/mL. What is the volume of
the bullet? - ANSWER: V=m/d
2.96mL
A metal object has a mass of 8.37 g. When it was placed in a graduated cylinder
containing 20.0 mL of water, the water level rose to 23.1 mL. What is the density of
the metal object? - ANSWER: d=m/v
2.7g/mL
Fahrenheit to Kelvin - ANSWER: Need celsius first
*C = *F - 32
-----------
1.8
then
*C + 273.15 = K
Define specific heat capacity and review the trends in specific heat capacity values. -
ANSWER: Specific heat capacity of a substance is the quantity of heat in joules
required to change 1g of the substance by 1*C
A copper medallion with a mass of 72.6 g initially at 21.5 °C was heated with 684 J of
heat. What is the final temperature of the copper medallion? - ANSWER: need the
SHC of copper = 0.385 J/g*C
then remember the formula:
q=m*C* delta T
Delta T = Tf-Ti
SO
Tf=Delta T + Ti
answer: 46.0*C
