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Homework 3
1) Which of the following are physical changes: ___________
and which are chemical changes: ____________
(a) melting of salt
(b) burning of wood
(c) evaporation of alcohol
(d) rusting of iron
(e) dissolving of sugar in water
____2) A chemical change always involves a change in
I) appearance
II) state
III) composition
IV) temperature
(a) I and II
(b) I, II and IV
(c) III only
(d) II and IV
(e) all of the above
____3) Choose the incorrect statement.
(a) matter is made of tiny units called atoms
(b) An element is a substance made of one type of atom
(c) A compound contains regions which are unlike other regions of the compound
(d) homogeneous mixture are solutions.
____4). Which of the following actions results in the formation of a heterogeneous mixture?
(a) mixing a gallon of blue paint with a quart of red paint
(b) mixing water and sand
(c) letting water evaporate in a completely closed jar
(d) mixing salt with water
(e) filling a balloon with air and helium
____5). Which equation given below does not follow the law of conservation of mass?
(a) 4 g methane + 16 g oxygen 11 g carbon dioxide + 9 g water
(b) 0.5 g hydrogen + 17.5 g chlorine  18 g hydrogen chloride
(c) 60 g carbon + 80 g oxygen  140 g carbon monoxide
(d) 63 g sulfur dioxide + 16 g oxygen 80 g sulfur trioxide
(e) 16 g methane + 64 g oxygen 44 g carbon dioxide + 36 g water
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____6) A 25g sample of sugar is found to contain 51.4% oxygen by mass. Another 250g sample
of the same sugar is also 51.4 % oxygen by mass. this is consistent with the:
(a) law of conservation of mass
(b) law of constant composition
(c) law of multiple proportion
____7). Any sample of hydrogen sulfide will contain 2 parts hydrogen and 32 parts
sulfur by mass. This means that ___ g of hydrogen and ___ g of sulfur will combine to
form ___ g of hydrogen sulfide.
(a) 1 g hydrogen, 16 g sulfur, 17 g hydrogen sulfide
(b) 2 g hydrogen, 16 g sulfur, 18 g hydrogen sulfide
(c) 1 g hydrogen, 16 g sulfur, 16 g hydrogen sulfide
(d) 2 g hydrogen, 30 g sulfur, 32 g hydrogen sulfide
(e) 2 g hydrogen, 34 g sulfur, 36 g hydrogen sulfide
____8) True or false:
Dalton's Atomic Theory states all of the following:
matter is made up from tiny, indestructible particles called atoms
the atoms of one element are all identical
that atoms of different elements have the same mass
(a) True
(b) False
____9) two samples of different compounds of nitrogen and oxygen have the following
compositions.
amount N
amount O
Compound A
1.75 g
2.00
Compound B
7.00g
4.00g
What is the ratio of nitrogen in compound A to compound B for a fixed amount of oxygen?
(a) 1:2
(b) 1:1
(c) 2:1
(d) 3:5
____10) Pick the wrong statement:
(a) Isotopes have different mass numbers but the same atomic number.
(b) Isotopes have the same mass number but different atomic numbers.
____11) Pick the correct statement:
(a) Atomic number is the sum of the number of protons and neutrons.
(b) Atomic number is the number of protons.
(c) The number of electrons are the atomic number of an atom.
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____12) which is the proper chemical symbol for tungsten?
(a) Te
(b) Ti
(c) Tm
(d) W
(e) Tc
____13) The nucleus of an atom is positively charged.
(a) True
(b) False
____14) What are the protons and neutrons that are emitted from a helium atom called?
(a) Alpha particles
(b) Beta particles
(c) Gamma rays
____15) Which statement is correct?
(a) Mass number is the sum of protons, neutrons and electrons in an atom.
(b) Mass number is the sum of protons and electrons in an atom.
(c) Mass number is the sum of protons and neutrons in an atom.
____16) An ion is a charged electron.
(a) true
(b) false
____17) As a result of Thomson's experiment with cathode-ray tubes,
(a) the mass of the electron could be measured.
(b) only one type of metal was shown to give off cathode rays or electrons.
(c) electrons were proposed to be in all atoms since many metals could emit cathode rays.
(d) the nuclei of atoms were discovered.
(e) the mass of atoms could now be measured.
____18). What was Thomson able to determine by measuring the deflection of cathode
rays in magnetic or electric fields?
(a) the mass of the metal atoms emitting the cathode rays
(b) the charge-to-mass ratio of protons
(c) the charge-to-mass ratio of electrons
(d) that atoms were made of electrons and concentrated areas of positive charge called
nuclei
(e) the charge of the nuclei giving off electrons in a cathode-ray tube
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____19). What causes the deflection of an alpha particle by the nucleus of a gold atom?
(a) the positive charge of the alpha particle and the positive charge of the nucleus
(b) the low mass of the nucleus
(c) the widespread distribution of mass in the atom
(d) the positive charge of the alpha particle and the negative charge of the nucleus
(e) the negative charge of the alpha particle and the positive charge of the nucleus
____20). Which of the following is true of a neutral atom?
(a) The number of protons + the number of neutrons = the number of electrons.
(b) The number of neutrons = the number of electrons.
(c) The number of protons = the number of neutrons + the number of electrons.
(d) The number of protons is = to the number of electrons.
(e) The number of neutrons = the number of protons.
____21). The charge of an anion is due to
(a) gaining a proton.
(b) losing an electron.
(c) sharing two electrons.
(d) gaining an electron.
(e) losing a proton.
22) Which of the following statement is true concerning the masses of individual Cl atoms?
(a) All atoms have a mass of 35.45 amu
(b) None of the atoms have a mass of 35.45 amu
(c) Some of the atoms have mass of 35.45 amu
(d) Most of the atoms have a mass of 35.45 amu
23) The total numbers of neutrons, protons, and electrons in the following species are?
number of neutrons
number of portons
number of electrons
31 3+
P
15
69
Ga
31
56 2+
26 Fe
24
Na
11
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24). What is the atomic weight of an unknown element A? if this element has three naturally
occurring isotopes: with the following natural abundance and isotopic mass.: isotope 1 (7.50 % ;
isotopic mass = 8.00 amu), isotope 2 (40.2 % ; isotopic mass = 8.05 amu) and isotope 3 (52.3%,
9.12 amu)?
25) The average atomic mass of Li is 6.94 amu. Lithium has only two stable forms Li-6 (6.01
amu) and Li-7 (7.01 amu). What is the natural percent abundance of Li-7?