chem Midterms
How many moles of ammonia are there in a 346 g sample of pure NH3 (17.03 g/mol)?
20.3 mol
Enriched weapons-grade uranium consists of 80% uranium-235 (235.044 u) and 20% uranium-238 (238.051 u). What is the average atomic mass of weapons-grade uranium, assuming the percentages are exact?
235.645 u
How many gold atoms are there in a 1.00 kg bar of gold (MAu = 196.97 g/mol)?
3.06 x 10^24
What is the energy (E, in J) of the photons emitted by an Ar+ laser with a wavelength of l = 488 nm?
4.07 x 10^-19 J
How much energy is required to ionize one mole of He+ ions in their ground state?
5,251 kJ
The Fe2+ transition metal ion has how many d electrons?
6
When 5.0 g of sulfur is combined with 5.0 g of oxygen, 10.0 g of sulfur dioxide is formed. What mass of oxygen would be required to convert 5.0 g of sulfur into sulfur trioxide?
7.5g
You are a You are a technician in an analytical laboratory and are asked to determine from its density whether an antique coin might be gold. You weigh the coin and find that its mass is 84.6419 g. When you place the coin in a graduated cylinder containing 105.53 mL of water, the water level rises to 114.64 mL. Calculate the density of the coin from your measurements and determine how many significant figures should be included in the reported result. Which one of the following numbers will you put in your report for the density of the coin?
9.29 g/mL
Which statement provides the best description of a covalent bond? Two or more electrons are attracted to each other, thereby holding the atoms together. A high electron density between two positively charged atomic nuclei serves to attract the nuclei to each other. The negative charge on one atom is attracted to the positive charge on a second atom. Two atomic nuclei are attracted to each other by the Coulomb force. Two atomic nuclei are attracted to each other by the strong nuclear force.
A high electron density between two positively charged atomic nuclei serves to attract the nuclei to each other.
Nitric acid and hydrochloric acid mix to form aqua regia that is capable of dissolving gold. What are the chemical formulas of these acids?
HNO3, HCl
The formula for a holmium sulfate compound is Ho(SO4)2. What would be the formula for a holmium phosphate compound given that the charge of holmium is the same in both compounds?
Ho3(PO4)4
BOUNS: O-S-S-O has three resonance Lewis structures that complete the octet for all the atoms. Which statements about these structures are correct? I. All are equivalent. II. All are nonequivalent. III. Two are equivalent, and one is nonequivalent. IV. The formal charges on all the atoms are zero in at least one structure. V. All the bonds have double-bond character.
III and V
Buf Buffer solutions that maintain certain levels of pH or acidity are widely used in biochemical experiments. One common buffer system uses potassium monohydrogenphosphate and potassium dihydrogenphosphate. What are the formulas of these two compounds?
K2HPO4 and KH2PO4
Which one of the following statements is not correct? -The composition of a mixture can vary. -A compound has a specific constant composition. -A compound has specific constant properties -The properties of a mixture can vary
Mixtures cannot be homogeneous
Which of the following molecules does not contain a triple bond? N2 CO C2H2 NO HCN
NO
Identify the binary compound that has polar bond and is a radical. Incorrect answer: CO H2O CaF2 NO2 N2O
NO2
Which anion is has an incorrect formula or is not named correctly? Cl- chloride All are named and labeled correctly. NO3- nitrite SO32- sulfite SO42- sulfate
NO3- nitrite
What is the formula for sodium nitride?
Na3N
12C, 13C, and 14C are examples of ________ because they have different numbers of ________.
isotopes; neutrons
Which of the following is a possible set of quantum numbers for a 3d orbital?
n=3, l=2, m= -1
Which combination of quantum numbers is possible for an atom with seven orbital orientations in one subshell?
n=5, l=3
What is the formal charge of each atom (from left to right) in the following resonance structure of SN2?
0, +1, -1
Which substance listed below contains the least oxygen atoms? 1 mol of N2O4 3 mol of CO2 2 mol of Al2O3 2 mol of HNO3 3 mol of Fe2O3
1 mol of N2O4
If the following operations are carried out, how would the final answer be reported? (14.1 + 12.14) x 7.45
195
Identify the correct statement regarding the mole: A mole consists of the number of particles in exactly 12 g of naturally occurring carbon A mole of ammonia gas (NH3) has a mass of 34.0 g. A mole of oxygen gas contains 6.02 x 1023 atoms A mole of chlorine gas contains 2 x 6.02 x 1023 atoms A mole of carbon dioxide contains two moles of oxygen molecules
A mole of chlorine gas contains 2 x 6.02 x 1023 atoms
Which of the following molecular ions has 5 total valence electrons? H2+ C2+ B2+ He2+ O2-
B2+
Which of the following is most likely to exhibit covalent bonding? Cs2O CO2 NaCl NaF CaCl2
CO2
Based on the element's position in the periodic table, which statement below is not correct? The charge on an ion of oxygen is 2−. Ca2+ has more electrons than Ar. The charge on an ion of chlorine is 1−. The charge on an ion of sodium is 1+. The charge on an ion of magnesium is 2+.
Ca2+ has more electrons than Ar.
Which of the following is most likely a polar covalent bond? K---F Na---Cl Mg---O Cl---O N---N
Cl---O
Which one of the following ionic compounds has an incorrect formula or is not named correctly? CoO, cobalt(II) oxide Cu2S, copper(I) sulfide Co3O2, tricobalt dioxide CoO2, cobalt(IV) oxide MgS, magnesium sulfide
Co3O2, tricobalt dioxide
Which one of the following statements is not correct? - Table salt (sodium chloride) is a compound - Air is a solution. - Helium is an element. - Water is a pure substance - Elements occur only in the form of individual atoms
Elements occur only in the form of individual atoms
Which of the following is an element? H2O NaCl HCl F2 MgO
F2
Which statement A-D about the reaction of methane with oxygen, which is called combustion and is represented by the reaction equation below, is not correct? The reaction products are carbon dioxide and water. CH4+2O2---->CO2+2H2O
Four atoms of hydrogen combine with four atoms of oxygen to produce water.
Which of these regions of the electromagnetic spectrum has the shortest wavelength?
Gamma rays
Indicate which molecule contains the largest number of lone-pair electrons. NO N2 H2 CO O2
O2
Which arrangement is in the correct order of decreasing radii? Ra > Li > Li+ Cs > Mn2+ > Mn P > P3- > As3- He+ > H Cr > Cr3+ > Ca Ra > Li > Li+
Ra > Li > Li+
Which of the following compounds has a tetrahedral geometry? BrF5 ICl3 PCl5 PH3 SiF4
SiF4
Which of the following is an alkaline earth metal? -Na -Al -Sr -K -Cu
Sr
Which statement best describes isotopes?
They have the same number of protons but a different number of neutrons
What is the ground state electron configuration for the most stable anion of selenium (Se)?
[Kr]
What types of bonds form between the bromine and oxygen atoms of the bromite ion (BrO2-) to minimize the formal charge?
between single and double
Name the following oxides of nitrogen in this sequence: N2O, NO, NO2, N2O4n in this sequence: N2O, NO, NO2, N2O4.
dinitrogen monoxide, nitrogen monoxide, nitrogen dioxide, dinitrogen tetroxide
Compared with the atomic radius of sulfur, the atomic radius oxygen of is ___________
smaller because the n quantum number decreases.
BOUNS: If each of the following metals is exposed to light with a wavelength of 240 nm, which will emit photoelectrons with the greatest kinetic energy?
sodium (4.4 x 10^-19 J)
How many atoms of each element are there in the compound Na3(PO4)?
sodium 3, phosphorus 1, oxygen 4
As a summer intern at the National Institute of Standards and Technology, a student performed three measurements to determine the density of water at 25℃ to four significant figures. She obtained the following results. The known density of water at 25℃ to three significant figures is 0.958 g/mL. trial 1: d=5.01 trial 2: d=4.95 trial 3: d=5.10 The measurements were ________
sufficiently precise but not accurate
Resonance structures indicate that ________
the electronic structure is an average or superposition of the diagrams.
Which one of the following is not a chemical reaction? iron rusting dynamite exploding wood burning eggs cooking water turning to steam
water turning to steam
