CHEMISTRY MID-TERM STUDY GUIDE --answers
For questions 1-6, determine the number of significant figures in each measurement.
__4___1) 4658 g
__2__ 3) 0.0020 km
___1__5) 200 m
__4___2) 360.0 cm
__3___4) 7.02x105 mm
___4__6) 8050. S
For questions 7-10, determine the number of significant figures in the calculated answers without
solving the problems.
__3___7) 4.033 X 8.99 =
__3___9) 34.6 + 22.22 =
__2___8) 0.330 / 5.6 =
___5__10) 22899 – 2 =
__d___11) In the measurement 305.67g, which digit is estimated?
a. The 3
b. The 0
c. The 6
d. The 7
__d___12) A piece of paper measures 220.5 cm by 76.3 cm. What is the area of this piece of paper
expressed to the correct number of sig. figs.?
a.
16824.15 cm2
b. 16824 cm2
c. 16820 cm2
d. 16800 cm2
__a___13) A sample of metal is found to have a density of 8.44 g/mL and a mass of 10.00g. What is
the volume of this metal?
a. 1.18 mL
b. 1.180 mL
c. 0.844 mL
d. 0.84 mL
___b__14) Calculate the density of a gas that has a volume of 1.033x10-2 L and a mass of 4.22x10-4 g.
a. 4.09x102 g/L
b. 4.09x10-2 g/L
c. 2.45x101 L/g
For questions 15 – 18 choose “A” if the statement refers to an ionic compound and “B” if the statement
refers to a covalent compound.
__B___15) Exist as neutral molecules.
__A___16) Made from a metallic and a nonmetallic element.
__B___17) Made from 2 or more nonmetallic elements.
__A___18) A crystal lattice structure with a very high melting point.
__c___19) How many dots does nitrogen have in its electron dot diagram?
a. 2
b. 4
c. 5
d. 7
__a___20) Which molecule’s central atom does not follow the octet rule?
a.
SF6
b. NO2
c. NH3
d. CBr4
__b___21) Which of the following is a nonpolar molecule?
a.
HCN
b. CBr4
c. NH3
d. H2O
__c___22) Which of the following elements exists as a diatomic molecule?
a. Ba
b. N
c. Cl
d. Ar
__ex___23) All atoms of the same element have the same:
a. number of protons
b. number of neutrons
c. mass number
d. mass
__ex___24) How do the isotopes hydrogen-2 and hydrogen-3 differ?
a. hydrogen-3 has one more electron than hydrogen -2. c. hydrogen-2 has three protons.
b. hydrogen-3 has two neutrons.
d. hydrogen-2 has no protons.
___ex__25) An atom of an element with atomic number 48 and mass number 120 contains
a. 48 protons, 48 electrons, and 72 neutrons.
c. 120 protons, 48 electrons, and 72 neutrons.
b. 72 protons, 48 electrons, and 48 neutrons.
d. 72 protons, 72 electrons, and 48 neutrons.
__ex___26) Which symbol correctly represents an element(D) whose atoms contain 15 protons and 20
neutrons?
a. 2015D
b. 1520D
c. 3515D
d. 1535D
__ex___27. The element argon contains the following isotopes with their relative abundance (RA) and
mass:
36
Ar (RA 0.337%; mass 35.978 amu); 38Ar (RA 0.063%; mass 37.963 amu); 40Ar (RA
99.600%; mass 39.962 amu). Calculate the average atomic mass of argon.
a. 37.967 amu
b. 35.978 amu
c. 38.000 amu
d. 39.947 amu
__b___28) Which of the following statements is correct?
a. Electrons are positively charged.
c. Protons are negatively charged.
b. Neutrons have no charge.
d. Atoms are positively charged.
__d___29) Which of the following statements is not consistent with the results obtained in
Rutherford’s gold foil experiment?
a. The nucleus of an atom is positively charged.
b. Atoms are composed mainly of empty space.
c. The nucleus contains all of the mass of the atom.
d. Electrons are contained in the nucleus of an atom.
__ex___30. After 252 days, a 24 g sample of scandium-42 contains only 3.0 g of the isotope. What is
the half-life of scandium?
a. 84 days
b. 10.5 days
c. 31.5 days
d. 126 days
For questions 31 – 38, match the correct formula with the correct name. If a name given does not
match a formula, place NA in the blank for not applicable.
a.
N2O5
b. KCl
c. Pb(NO3)2
d. CO2
e. V2S5
__c___31) Lead (II) nitrate
__a___32) dinitrogen pentoxide
__NA___33) Lead nitrate
__NA___34) potassium (I) chloride
__b___35) Potassium chloride
__d___36) carbon dioxide
__NA___37) vanadium (II) sulfide
__e___38) vanadium (V) sulfide
__c___39) Which of the compounds listed below contains the Fe
a.
FeO
b. FeF2
c. Fe2O3
3+
ion?
d. FeSO4
__c___40) Which statement best describes a group 2 element such as barium?
a. Forms a cation by gaining 2 electrons.
b. Forms an anion by losing 2 electrons.
c. Forms a cation by losing 2 electrons.
d. Forms an anion by gaining 2 electrons.
For questions 41-44, match the correct formula with the correct name.
a.
HCl
b. HClO
c. HClO3
d. HClO2
__c___41) chloric acid
__a___42) hydrochloric acid
__d___43) chlorous acid
__b___44) hypochlorous acid
For questions 45 – 49 select: true (T) or false (F):
__T___45) In an electron configuration, sublevels are filled in order of increasing energy.
__F___46) The “p” orbitals are found in every energy level.
__T___47) The total number of electrons in a configuration can be determined by adding the
superscripted numbers.
__F___48) The abbreviated electron configuration of osmium (Os) would start with [Kr].
__T___49) The “d” orbitals can hold a maximum of 10 electrons.
OPEN-ENDED SECTION: Please answer on a separate sheet of paper.
1. Draw a Lewis dot diagram for PCl3, identify its shape and molecular polarity.
2. Name the following compounds: CS2 and Sn(BrO3)2. Identify each as either ionic or molecular and
explain, in detail, the differences in how each one is named.
1.
..
..
..
: Cl - P – Cl:
.. | ..
:Cl:
..
Trigonal pyramid and polar
2. The compound with the formula CS2 is called carbon disulfide. The fact that the formula
consists of the symbols of two nonmetallic elements identifies this compound as a molecular
substance and is therefore named using the traditional or prefix system. The prefix “di” was
selected to indicate the presence of 2 sulfur atoms; since there is only one carbon atom and it is
listed first in the formula the “mono” prefix is not used.
The compound Sn(BrO3)2 contains a metallic element (Sn) and a polyatomic ion (BrO3) in its
formula and this identifies it as an ionic compound. Therefore, Sn(BrO3)2 can be named either
tin(II) bromate in the Stock system where the (II) indicates the charge on the tin cation to be
2+; or stannous bromate in the traditional system where the “ous” suffix indicates tin in its lower
oxidation or charge of 2+.
3a. Energy to raise the temperature of the ice from -10.0oC to 0oC:
H = m x Δt x Cp(ice)
H = (400.0 g) (10.0oC)(2.06J/g·oC) = 8240 J
b. Energy to melt ice:
400.0 g x 335 J/g = 134000 J
c. Energy to warm the liquid water from 0oC to 60.0 oC:
H = m x Δt x Cp(liquid)
H = (400.0 g)(60.0 oC)(4.18 J/g·oC) = 100320 J = 1.00 x 105 J
d. total energy:
H = 8240 J + 134000 J + 1.00 x 105 J
H = 242240 J = 242000 J