Chem
Which potassium salt if 28.9% by mass?
KClO3
How many sulfur atoms are in 3.00g of iron pyrite, FeS2 (M=120.0)
3.01*10^22
1.0000g of a transition metal carbonate, MCO3, is heated to produce the metal oxide and 0.383 of carbon dioxide. What is the identity of metal M?
Mn
In which set are all three species isoelectronic?
Se2-, Br, Rb+
Which principle restricts the occupancy of an atomic orbital to no more than two electrons?
The Pauli exclusion principle
Which is the best explanation for phosphorus favoring formation of P4 over P2 molecules, while
the larger size of phosphorus allows the bonding electrons to be closer together.
Polypropylene is made by polymerizing propene, C3H6 (M = 42.1). How many molecules of propene must be polymerized to make 3.50 g polypropylene?
5.01*10^22
An organic compound contains only carbon, hydrogen, nitrogen, and oxygen. it is 61.71%C, 4.03%H, and 16.00% N by mass. what is its empirical formula?
C9H7N2O2
1.00 g of hydrated potassium carbonate, K2CO3•nH2O, is heated to 250 °C to give 0.836 g anhydrous K2CO3. What is the value of n?
1.0
When substances are separated by fractional distillation, which property is least typical of the substance that distills first?
highest molar mass
Which element is the most abundant (by mass) in the Earth's crust
Oxygen
A student determines the number of moles of water in a hydrated metal oxide by weighing a clean, dry crucible and lid while the crucible is empty, then reweighing the crucible and lid with a sample of the hydrate, heating the crucible and lid with a Bunsen burner and then reweighing the crucible and lid with the sample after cooling to room temperature. Which error will result in too high a value for the amount of water of hydration?
Some of the heated oxide is spilled from the crucible before it can be weighed.
The diagram is a microscopic view of a snapshot of a substance at equilibrium, with the circles representing molecules and the arrows the molecules' velocities. What state of matter is depicted?
liquid
Which ground-state electron configuration of gas-phase Co2+
Ya me la se
A fluorescent dye absorbs a photon of light of 485 nm and emits a photon of light at 540 nm. How much energy is lost as heat?
4.17 × 10^-20 J
Which gas-phase atom releases the most energy when an electron is added to it?
Cl
which is a possible set of quantum numbers n, l, ml, ms for a valence electron of Sulfur (S)
3 ,1, -1, 1/2
Which period 3 element has these successive ionization energies (in kJ mol-1 )?
Si
Which structure best depicts the three-dimensional shape of the P4 molecule?
Diamond shape
which element is NOT present in DNA
S
A 1.00-g sample of which compound will produce the greatest amount of carbon dioxide after complete combustion with excess oxygen?
C6H6
Acetanilide (C6H5NHCOCH3, M=135.2) can be prepared from aniline (C6H5NH2, M+93.1) and acetic anhydride ([CH3CO]2O, M=102.1) according to the balanced equation below
C6H5NH2 + (CH3CO)2O -> C6H5NHCOCH3 +CH3COOH
If 10.0 g acetanilide is isolated from the reaction of 10.0g aniline with 10.0g acetic anhydride, what is the percent yield of the reaction?
69.3%
what is the main purpose of adding boiling chips to a solution that will ____________
To prevent the solution from super heating
A cotton ball burns more brightly in a jar of 80% O2 than in the air, which is 20% O2. Which is the best explanation for this observation?
The cotton collides more frequently with the O2 inside the jar.
Which species has the largest ionic radius?
S2-
which of the following statements regarding ionization energy of gas is correct?
Pendiente
Which molecule has the shortest bond?
H2
How many completely filled p orbitals are present in a ground state Cl atoms
5
The electronegativity of gallium (1.8) is greater than that of aluminum (1.6). Which is the best explanation for this difference?
Ga is larger than Al, so its valence electrons experience less electron-electron repulsion
Which molecule has no unpaired electrons
SO2
The bond distance in CO is 112.8 pm, while the bond distance in NO is 115 pm. Which is the best explanation for the shorter bond in CO?
Carbon has one fewer valence electron than nitrogen
Which hydrocarbon is 84.1% carbon by mass?
C8H18
Lithium hydrogen carbonate, LiHCO3, decomposes when heated to form Li2O, CO2, and H2O. How many moles of H2O are formed when 0.50 mol LiHCO3 decomposes?
0.25
A solution of which compound gives a violet flame test?
KNO3
When the chemical equation is balanced what is the ratio of the coefficient of Ag(s) to the cofficient of H2O(l)?___Ag(s)+____NO3-(aq)+____H+(aq) -> ___Ag+(aq)+____NO(g)+______H2O(l)
3:2
which statement regarding the relative energies of monochromatic light with λ = 800 nm and monochromatic light with λ = 400 nm is correct?
800 nm light has twice as much energy per mole of photons as 400 nm light.
Which gas-phase atoms in their ground states are
diamagnetic?
I. Fe
II. Zn
Both I an II
The boiling points of the alkali metals decrease from lithium to cesium. Which trend is most closely related to the decreasing boiling points?
Decreasing electron affinity down the group
Which aspect of metallic bonding best accounts for the characteristic malleability of metals?
Metals contain delocalized electron
How many oxygen atoms are in 225g of O2?
8.47x10^24
What state of matter corresponds to the diagram below
Gas
Why is the equation incorrect?Mg3 + N2 → Mg3N2
Some of the subscripts are incorrectly used
A lithium carbide (LixCy) reacts with water as follows:
LixCy + H2O -> LiOH + C2H2 (unbalanced)
What is the simplest formula of the carbide?
LiC
Which metal reacts most vigorously with water?
K
The molar mass of a volatile liquid (bp<90*C) is to be determined by measuring the density of its vapor in an Erlenmeyer flask capped with Al foil with a pinhole to allow the vapor to escape. A sample of the liquid is added to the pre-weighed flask that is heated in a water bath until the liquid has evaporated, after which the flask is dried and reweighed. Which piece of information is not required to determine the molar mass of the liquid?
mass of liquid sample
How many millimoles of methane, CH4, are present in 6.4g of this gas
4.0 x 10^2
Which list includes elements in order of increasing metallic character?
Br, Se, As
Which species has a Lewis diagram and structure most like that of the carbonate ion, CO32−?
NO^3−
Which technique is recommended for determining the odor of an unknown liquid in the laboratory?
Use a hand to fan some of the vapor from the test tube to the nose and inhale
Which separation technique is based on differences in the volatility of the substances to be separated?
destillation
Which set contains only covalently bonded molecules
BCl3, SiCl4, PCl3
Which statement about silicon is false?
It is extremely rare in the earth's crust
Hexane, C6H14, is immiscible with water and ethanol. Water and ethanol are miscible. C6H14 has the lowest density. Which diagram represents the results when equal volumes of these three lipid are placed in a test tube and shaken?
3
for which substance is the oxidation number of vanadium the same as that in the VO3- ion
VF5
Which property decreases from left to right across the periodic table and increases from top to bottom?
atomic radius
According to the Aufbau principle, which is the sequential order of filling subshells in a ground state atom
3p 4s 3d
which pair of elements have chemical properties that are the most similar
Al and Ga
Which Lewis dot structure is the best representation of the bonding in the thiocyanate ion SCN-?
view the video
Which Lewis dot structure is the best representation of the bonding in the thiocyanate ion SCN-?
5
Five pellets of metal have a total mass of 1.25 g and a total volume of 0.278 mL. What is the density of the metal in g mL-1 ?
4.5
Selenium (Se) is similar to sulfur in its properties and francium (Fr) is an alkali metal. What is the formula for francium selenite?
Fr2SeO3
Which letter in the diagram depicts the hottest portion of a Bunsen burner flame?
D
What volume of liquid A has the same mass as 80.0 cm3 of liquid B?
193 cm3
A monoatomic Ion that has 18 electrons and a +2 charge:
is isoelectronic with Ar
Naturally occurring thallium consists of two stable isotopes, Tl-203 and Tl-205 (atomic masses =203.0 and 205.0, respectively) and has an average atomic mass of 204.4. What is the percentage of Tl-205?
70.0%
What is the maximum mass (in grams) of NO that could be obtained from 15.5 g of N2O4 and 4.68 g of N2H4 when they react? The balanced chemical equation is :
2N2O4+N2H4⟶6NO+2H2O
15.2
Which pair of symbols represent nuclei that have the same number of neutrons?
A
The conversion of glucose to ethanol is represented:
x C6H12O6 ---> y C2H6O+ z CO2
What are the coefficients x, y, z, respectively, in the
balanced equation?
1, 2, 2
How many orbitals have the quantum numbers: n=4, l=3, ml=0
3
what is the hybridization of the carbon atoms of C2H4 (ethane)
sp2
A 1.0 gram sample of which substance contains the largest number of molecules?
CH3Cl
A student wishes to determine the thickness of a rectangular piece of aluminium foil but cannot measure it directly. She can measure its density (d), length (I), mass (m) and width (w). Which relationship will give the thickness?
m/d⋅l⋅w
liquids exhibit all these properties except
definite shape
which properties of electromagnetic radiation are inversely related?
energy and wavelength
What are the hybridization of the carbon atoms labeled
and respectively in glycine?
sp3 sp3 (D)
A student is asked to measure 30.0 g of methanol (d = 0.7914 g/mL at 25˚C) but has only a graduated cylinder with which to measure it. What volume of methanol should the student use to obtain the required 30.0 g?
37.9 ml
Enzymes convert glucose (M= 180.2) to ethanol (M= 46.1) according to the equation C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂ What is the maximum mass of ethanol that can be made from 15.5 kg of glucose?
7.93 kg
A student is asked to dispense 24.70 mL of a solution with an uncertainty of less than 0.05 mL. Which item should be used for this task?
50 mL buret
Oxygen gas can be produced by the decomposition of all of the following substances EXCEPT
calcium oxide.
Which gaseous product is formed when dilute nitric acid reacts with silver metal in the absence of air?
NO
which oxidation number of rhenium in Ca(ReO4)2
+7
The molar mass of an unknown organic liquid (M - 100) is determined by placing 5 mL of the liquid in a weighted 125 mL conical flask fitted with a piece of Al foil with a pinhole in it. The flask is heated in a boiling water bath until the liquid evaporates to expel the air and fill the flask with the unknown vapor at atmospheric pressure. After cooling to room temperature the flask and its contents are reweighed. The uncertainty in which piece of apparatus causes the largest percentage error in the molar mass :
balance(± 0.01 g)
which lewis dot structure is a valid representation for the sulfite ion
view video
A triple bond is found in which of the following species
I.CO
II. C2H2
III. CN-
I, II, III
A solid can be separated from a liquid by all the following means EXCEPT
hydration
A student determined the density of a solid to be 2.90, 2.91 and 2.93 g-cm-3 • If the actual density of this solid is 2.70 g-cm-3 , how should the student's results be described?
low accuracy and high precision
The ion 55Mn2+ contains which combination of protons, neutrons and electrons?
A
On the basis of VSEPR theory, what geometry is predicted for the central sulfur atom in SOCl2?
trigonal pyramid
In the above diagram, the paired open spheres represent H2 molecules and the paired solid spheres represent N2 molecules. When the molecules in the box react to form the maximum possible amount of ammonia (NH3) molecules, what is the limiting reactant and how many molecules of NH3 can be formed?
N2 is limiting. 10 molecules of NH3 can be formed.
A student is asked to analyze a water sample from a stream for total solids (TS), dissolved solids (DS) and suspended solids (SS). She carries out the experiments below.
1. A 25-mL portion of the water sample is evaporated to dryness in a pre-weighed evaporating dish to give mass 1 .(
2. A separate 25-mL portion is filtered into a second pre-weighed evaporating dish and evaporated to dryness to give mass 2
.How are values for TS, SS and DS (per 25 mL water) determined?
TS= mass 1, SS= mass 1- mass 2, DS= mass 2
Benzene, C6H6, reacts with oxygen, O2, to form CO2 and H2O. How much O2 is required for the complete combustion of 1.0 mol C6H6?
7.5 mol
A 10.00 g sample of a soluble barium salt is treated with an excess of sodium sulphate to precipitate 11.21g BaSO(M=233.4). Which barium salt is it?
BaCl2 (M=208.2)
The formula for terbium phosphate is TbPO4. The formula for terbium sulphate is:
Tb2(SO4)3
Which statement about bonding is correct
A o bond has cylindrical symmetry about the bonding axis
Which 50-mL container would be most suitable for measuring and dispensing 37mL of an aqueous solution?
D
Which of the following statements is best supported by the data from Rutherford's experiment of scattering alpha particles with a thin metal foil?
The mass and positive charge of an atom
Barium chloride reacts with sodium sulfate according to the following equation:
BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2 NaCl(aq)
A student mixes a solution containing 10.0 g BaCl2 (M = 208.2) with a solution containing 10.0 g Na2SO4 (M = 142.1) and obtains 12.0 g BaSO4 (M = 233.2). What is the percent yield of this reaction?
The isolated barium sulfate is most likely wet, since the yield would otherwise be greater than 100%
Which best describes the bonding in Cu(s)?
The Copper Atoms are positively charged in a sea of delocalized electrons
Which particle consists of 13 protons, 14 neutrons, and 10 electrons?
aluminum ion
Enzymes convert glucose (M = 180.2) to ethanol (M = 46.1) according to the equation
C6H12O6⟶2C2H5OH+2CO2
What is the maximum mass of ethanol that can b made from 15.5 kg of glucose?
7.93 kg