Ms. Belcoure’s Mid-Term

How many significant figures are there in 0.732 m.
3
Define matter
Something with both mass and volume
Is soil a homogeneous or heterogeneous mixture?
heterogeneous
How are mixtures separated?
By using physical properties
What physical property is being taken advantage of in the distillation process?
boiling point
What does the arrow in a chemical reaction signify?
the direction the reaction is going in
What is a qualitative observation?
An observation without numbers.
What is a quantitative observation?
An observation with numbers. A measurement.
What is an accurate measurement?
A measurement that comes close to the true value.
What is a precise measurement?
A measurement that comes close to several previous measurements.
Can a measurement be precise but not accurate?
Yes
When using scientific notation the exponent indicates how many times the coefficient must be multiplied by 10. Which way does the decimal point move if the exponent is negative?
To the left.
Which way will you move the decimal if the exponent is positive?
To the right.
What are included as significant figures when doing a scientific measurement?
All the digits that are known precisely (There are usually lines for these.) plus one last digit that is estimated.
How many significant figures are there in 7004 m.
4
How many significant figures are there in 0.0056 m.
2
How many significant figures are there in 700 m.
One, unless the zeros are measured values.
How many nanometers are in a meter?
1,000,000,000
Express the following answer in scientific notation with the correct number of significant figures. 7.8g + 34.15g + 19g =
6.1 x 10^1 g
Define density.
Mass divided by Volume
A 35.0 mL metal cube weighed 242.455g. What is its density? Answer with the correct number of significant figures.
6.93 mL/g
A substance is described as hard, is that a qualitative or quantitative description?
Qualitative
Each element on the periodic table has two numbers. What is the smaller number called?
Atomic Number
Each element on the periodic table has two numbers. What is the larger number called?
Mass Number
What does the Atomic Number tell us about subatomic particles?
The number of protons equals the atomic number.
How would you calculate the number of neutrons from the periodic table?
Mass Number – Atomic Number = Number of Neutrons
How much do electrons affect the Mass Number?
They don’t, their mass is negligible.
When is an atom an isotope?
Elements with the same number of protons but a different number of neutrons.
What is the atomic number of radium?
88
What is the mass number of radium-226?
226
Determine the number of neutrons in radium-226.
138 neutrons (Subtract the atomic number from the mass number.)
What are the horizontal rows on the periodic table called?
periods
How many valence electrons does a helium atom have?
2
Are these the questions that make up Ms. Belcoure’s final?
No, but this is the content you need to know for that final.
What are the vertical columns on the periodic table called?
groups or families
Are most elements metals or non-metals?
metals
Which blocks make-up the representative elements?
s and p
What makes the electron configurations unique in the representative elements?
the outermost s and p sublevels are partially filled
As we move across a period in the periodic table what subatomic particle is added?
proton
As we move across the periodic table one proton is added to each element. What other subatomic element must be added if the atom is to remain neutral?
electron
What is added as we move down a group?
energy level

Nitrogen’s electron configuration is 1s2 2s2 2p3. How many electrons are in the outermost sublevel of Phosphorus?

(CLUE: Not energy level, sublevel.)

3
Which is a transition metal? sodium, iodine, nickel or uranium(Know why, these aren’t the ones on the test.)
nickel
Which is an inner transition metal? sodium, iodine, nickel or uranium(Know why, these aren’t the ones on the test.)
uranium
Of the three subatomic particles, the electron plays the greatest part in determining the physical and chemical properties of an element. What sublevel is being filled as we move, left to right, along the transition metals.
d
The arrangement of elements in the periodic table depends on physical and chemical properties. Therefore, there is a relationship between the electron configuration of an element and its position on the table. What sublevel is being filled as we move, left to right, along the inner transition metals.
f
Atomic radius increases as we move down a group. Why?
Another energy level is filled which increases the size of the electron cloud.
State the main premise of the law of conservation of mass.
matter cannot be created or destroyed in a chemical reaction
What subatomic particle is lost to form a cation?
electron
What force holds electrons to the atom?
positive protons, electromagnetic
Which has the largest radius, neutral calcium or its ion? (Know why, this isn’t the one on the test?)
neutral calcium
Metals are on which side of the stair-cased line?
left
What is electronegativity?
an atom’s ability to attract electrons
Which element has the highest electronegativity? Fe, Cl, B, Cs (Know why, these are not the one’s on the test.)
Cl
Which element would you expect to have the properties most like carbon? (Again, know why.)
silicon
What is most of the volume in any atom?
empty space
A nuclear particle that has about the same mass as a proton, but with no electrical charge, is called a(n)…
neutron
What is the nucleus, except a common isotope of hydrogen, made up of?
tightly packed protons and neutrons
An isotope of titanium consists of 22 protons, 22 electrons, and 25 neutrons. What is its mass number?
47 (Again, the element on the test is not this one.)
Isotopes are atoms of the same element that have different…
number of neutrons
Write the Lewis dot structure for potassium.
there should be one dot (Be sure you can do all the representative elements)
What is the name given to the electrons in the highest occupied energy level of an atom?
valence electrons
How are the noble gasses unique?
the outermost s and p sublevels are completely filled
The octet rule means atoms react to imitate __________.
the electron configuration of a noble gas
How does lithium obey the octet rule when reacting to form an ionic compound?
it loses one electron
What is calcium’s oxidation number?
+2
What ion does oxygen become when reacting with a metal?
anion, -2
Which kind of ion does neon become when reacting with a metal?
Trick Question, none of the noble gasses form ions
How many electrons must nitrogen gain to achieve a noble gas electron configuration?
3
How many electrons must barium give up to achieve a noble gas electron configuration?
2
What is bromine’s oxidation number?
-1
Will carbon and oxygen form an ionic compound?
no
Will lithium and oxygen form an ionic compound?
yes
What is a polyatomic ion?
two or more atoms, covalently bonded with a charge
What is a salt?
an ionic compound
What type of bond shares electrons?
covalent
What type of bond is formed between anions and cations?
ionic
What state are ionic compounds usually in at room temperature?
solid
Melting points are good indicators of bond strength. The higher the melting point of a compound the stronger the bond. The melting point of sodium chloride is relatively _____________.
high
An element’s chemical properties are determined by __________________.
valence
Which is the most reactive? Li, B, C, Ne
Li
What is the mass of aluminum-27 isotope?
27
Which electron configuration belongs to the element that is the most chemically reactive? 1s22s22p63s23p6, 1s22s22p5, 1s22s22p6, 1s2
1s22s22p5
Which group of elements is inert?
noble gasses
What will cause the element with the electron configuration 1s22s22p63s23p4 to have an octet configuration?
gain 2 electrons
Which of the following is NOT matter? atoms, ultraviolet radiation, air, the Sun
ultrviolet radiation
What element has 5 protons and 6 neutrons?
boron
What is the branch of chemistry that focuses on carbon-containing chemicals called?
organic chemistry
What neutral atom has 88 electrons?
radium
Which is poured first when preparing an acid solution, acid or water?
water,add acid to water slowly
What element has an atomic number of 78?
platinum
How many significant figures are in the value 213 000 m/s
3
If you need to write 215 000 g in scientific notation, how many significant figures should be included.
It has three significant figures
Write 319 000 000 in scientific notation.
3.19 x 10^8
Round 12.655 cm to four significant figures.
12.66 cm
Which is a compound salt, air, or nickel?
salt
How many electrons does Osmium-190 have?
76
Which of the following is a homogeneous mixture, silicon, air, nickel?
air
How do you know a reaction is exothermic?
it releases energy, usually in the form of heat
Which of the following is an element salt, brass aluminum?
aluminum
Elements of the same group have the same number of ______________?
valence electrons

Most of the elements in groups 6A-8A are classified as ______________.

;

Clue:noble gases are 8A, halogens are 7A

nonmetals
Is RbI ionic?
yes
Identify the period and group of the element that has the electron configuration [Ne]3s2 3p3.
period 3, group 5A
An element with the electron configuration 1s22s22p63s2 will ionize to a(n)…
cation
Is the following electron configuration stable or unstable, [Ar}4s^2 3d^10 4p^5
unstable
Is the following electron configuration a metal or a non-metal, [Ar}4s2 3d10 4p5
non-metal
What is the electron configuration for the element in group 4A and period 4 of the periodic table?
[Ar]4s^2 3d^10 4p^2
What should you use to measure volume?
a graduated cylinder, or you could use a ruler and calculate the volume
The trend in the atomic radii as you move doewn the group 1A elements is partially due to ____________.
shielding by inner electrons
Which is larger, Br or Br.
Br-
What units are used to express volume?
liters, milliliters or cm^3
How many electrons does an atom generally need in its outer level to be the most stable?
8
An element with the electron configuration 1s2 2s2 2p6 3s2 will ionize to a(n);
cation
Elements in the same group have similar chemical properties because…
they have the same number of valence electrons.
What electrons are involved in the formation of a covalent bond?
shared valence electrons
Describe the relationship between boron and silicon.
They have a diagonal relationship.
What is the value of all conversion factors?
1
Name three elements found most frequently in living organisms?
carbon, nitrogen, and oxygen
How many moles are 1.2 x 1024 molecules of CH4?
2.0 moles CH4
Is the following electron configuration a nobel gas, ns^2 np^6? (where n equals one through seven)
yes
How many formula units are in 2.3 moles of NaCl?
1.4 x 10^24 formula units NaCl
How many outer d electrons are there in an ion that has achieved a pseudo-noble gas configuration?
ten
In a chemical equation where are catalysts written?
above the arrow
What is the formula of calcium phosphate?
Ca3(PO4)2
What are the diatomic seven?
hydrogen, nitrogen, oxygen, florine, chlorine, bromine, iodine
How many electrons are shared in a double bond?
four
When balancing a chemical reaction there is only one type of number that can be changed. What do we call them?
coefficients
A mole of potassium chloride (KCl) contains 6.02 x 1023 ____________.
formula units
The SI unit of molar mass is the ______.
grams/mole
How many moles of oxygen atoms do 1.5 moles of CO2 contain?
3.0 mol
Which has the smallest molar mass: CO, CO2, H2O, H2O2 ?
H2O
One mole of silicon(Si) has a mass of 28.086 g, and one mole of carbon has a mass of 12.011 g. What is the mass of one mole of silicon carbide (SiC)?
40.097g
The correct Lewis structure for a molecule of the compound C2H2 contains how many double bonds?
1
Methane (CH4) contains 75% carbon. What percentage of methane is hydrogen?
25%
Write the chemical formula for sodium bromide dihydrate.
NaBr*2H2O
Is bromine stable or unstable?
stable, because it is neutral
What are units of concentration?
moles
Stoichiometry is bases on what law?
conservation of mass
What is molar mass?
The sum of the masses of all the atoms in a compound
Where do you look to find mole ratios for a reaction?
balanced chemical reaction
In the decomposition reaction AB into substances A and B, what is the number of mole ratios?
6
1.73 moles of an Ideal Gas has a pressure of 365.38 torr, at 272.6 Kelvin. Using the constant 62.36 L(torr/mol K), what is its volume?
80.5L
What will an acid produce in water?
H+ or H3O+, hydronium ions
Find the mass in grams of 2.23 x 1024 atoms of nitrogen.
51.8 g N
Is bromine and metal or nonmetal?
nonmetal
What is the most important industrial chemical in the world?
H2SO4, sufuric acid
List the 3 most studied types of radiation from most massive to least massive.
alpha, beta, gamma
What is the majority of an atom’s volume occupied by?
nothing, empty space
Define exothermic reactions.
Exothermic reactions release energy into the environment.
In a fusion reaction would you expect the product(s) to have more or less mass than the reactant(s)?
more
Write the name for Ca(OH)2?
calcium hydroxide
In a fission reaction would you expect the product(s) to have more or less mass than the reactant(s)?
less
What is the electron configuration of the element in group 4A and period 4 of the periodic table?
[Ar]4s23d104p2
What type of radioactive decay is not a particle?
gamma
Which family of elements are inert?
noble gases
Are half lives the same for different isotopes?
No, different isotopes have different half lives.
What element is [Ar]4s23d104p5 ?
Br
What happens to the size of atoms as you go down a group?
The size increases
What is the product when magnesium is burned in oxygen?
MgO
What would be the correct coefficients in the chemical equation of Mg reacting with oxygen?
2,1,2
What will a base produce in water?
OH-, hydroxide ions
Give two reasons the size of an atom increases as you move down a group.

1. Each has a new principal energy level.

2. shielding by inner electrons

Name 2 things that are not matter?
energy, forces, light, emotions
Is air matter? Why?
Yes, because it has volume and mass.
Is H2CO3 an acid or a base? Why?
acid: because it will donate a proton
Why do chemists do titrations?
to determine the concentration of an unknown
What is potassiums oxidation number?
1+
Is NaF ionic or covalent?
ionic

Which is most stable:

[Ne]3s23p5

[Ne]3s23p64s23d5

[He]2s22p3

[Ne]3s23p6

[Ne]3s23p6
Is SO2 ionic or covalent?
covalent
How does a covalent bond differ from an ionic bond?
Ionic bonds result from the transfer of electrons. Covalent bonds result from the sharing of electrons.
Elements in the same group have the same number of ________________.
valence electrons
Are groups 6A through 8A be in the metals or nonmetals side of the periodic table?
non-metals
Identify the period and group of the element that has the electron configuration [Ne]3s23p3.
period 3, group 5A
x

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