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WorksheetsPNCO 2023 School-Level Eliminations
Total questions: 50
Worksheet time: 32mins
In mammals, lactose (milk sugar) is metabolized to glucose (C6HI206), the key nutrient for generating chemical potential energy. How many grams of carbon are in 16.55 g of glucose?
6.62 g
9.93 g
4.14 g
12.41 g
Elemental analysis of a sample of an ionic compound showed 2.82 g of Na, 4.35 g of Ct, and 7.83 g of 0. What is the empirical formula and name of the compound? Atomic Masses: Na: 22.99 g/mol, Cl: 35.45 g/mol, O: 16.00 g/mol
NaClO
Na2ClO2
NaClO2
NaClO4
Na2ClO4
Within the cylinders of a car's engine, the hydrocarbon octane (C8H18), one of many components of gasoline, mixes with oxygen from the air and burns to form carbon dioxide and water vapor. What are the coefficients (arranged in order of appearance) in the balanced equation for the complete combustion of octane?
_ C8H18 + _ O2 → _ CO2 + _H2O
1, 12, 8, 9
1, 24, 8, 9
2, 25, 16, 18
2, 12, 8, 9
2, 24, 16, 18
Copper is obtained from sulfide ores, such as chalcocite, or Copper(I) Sulfide, by a multistep process. After an initial grinding, the first step is to "roast" the ore (heat it strongly with oxygen gas) to form powdered Copper(I) oxide and gaseous sulfur dioxide. How many grams of sulfur dioxide are formed when 10.0 mol of copper(I) sulfide is roasted? The molar mass of SO2 is 64.04 g/mol.
320.4 g
640.7 g
1281 g
12.81 g
A fuel mixture used in the early days of rocketry is composed of two liquids, hydrazine (N2H4) and dinitrogen tetraoxide (N2O4), which ignite on contact to form nitrogen gas (N2) and water vapor (H2O). How many grams of nitrogen gas form when 100 g of N2H4 and 2.00 x 200 g of N2O4 are mixed?
65.6 g
182 g
131 g
91.6 g
How many hydrogen atoms are in 2.50 g of pharmacolite, CaHAsO4•2H2O (Molar Mass = 216.0)?
6.97 × 1021
2.09 × 1022
2.79 × 1022
3.48 × 1022
A 2.50 L sample of butane gas (C4H10), measured at 22.0 ºC and 1.20 atm pressure, is combusted completely and the carbon dioxide gas collected at the same pressure and temperature. What volume of CO2 is produced?
2.50 L
9.00 L
10.0 L
22.5 L
What volume of 18.0 M sulfuric acid must be diluted to 250.0 mL to afford a 0.55 M solution of sulfuric acid?
3.1 mL
4.5 mL
7.6 mL
31 mL
What is the concentration of H2O2 in a solution that is 30.0% by mass hydrogen peroxide and has a density of 1.11 g/mL?
9.79 M
12.6 M
18.5 M
32.6 M
Which ion gives a blue solution?
Cu2+
Zn2+
Fe3+
Ni2+
Co2+
A student is using a buret for a titration. What initial buret reading should be recorded?
6.6 mL
6.63 mL
7.4 mL
7.37
A strip of metallic zinc is placed in a beaker containing dilute aqueous copper(II) nitrate. Which statement correctly describes what takes place?
No reaction takes place.
The mass of the metal strip decreases as the zinc is oxidized.
A white precipitate of CuNO3 is formed.
Bubbles of NO(g) form as the nitrate ion is reduced.
Which element does NOT have multiple allotropes?
Carbon
Oxygen
Fluorine
Phosphorus
The molar mass of a volatile organic liquid is measured by weighing the mass of an empty flask of known volume, adding some of the liquid, heating the flask in a water bath until the liquid has just vaporized completely, then sealing the flask, letting it cool, and remeasuring the mass of the flask with the remaining organic compound. Which error will lead to a calculated value of the molar mass that is lower than the theoretical value?
The flask is not sealed promptly after the last of the compound vaporizes
The organic compound dimerizes to an appreciable extent in the gas phase.
The barometric pressure was assumed to be 1 atm but in fact was greater than 1 atm.
The volume of the flask used in the calculation is smaller than the true volume.
Which compound has the highest normal boiling point?
1-butanol, CH3CH2CH2CH2OH
2-butanol, CH3CH2CH(CH3)OH
2-methyl-1-propanol, (CH3)2CHCH2OH
2-methyl-2-propanol, (CH3)3COH
A portion of the phase diagram of elemental sulfur is shown below. Which statement about sulfur is correct?
Rhombic sulfur cannot be sublimed without first converting to monoclinic sulfur.
The conversion of rhombic sulfur to monoclinic sulfur is exothermic.
Rhombic sulfur is denser than monoclinic sulfur.
At atmospheric pressure, monoclinic sulfur cannot be in equilibrium with liquid sulfur.
A reaction has Keq = 20 at 298 K, and Keq increases with increasing temperature between 298 K and 350 K. What may be concluded from these observations?
I. ∆G°rxn < 0 at 330 K
II. ∆S°rxn > 0 at 330 K
I only
II only
Both I and II
Neither I nor II
In a study of the reaction below, the concentration of O2(g) is found to be decreasing by 0.042 M⋅min-1. At what rate is the concentration of nitrogen dioxide gas changing?
2 NO(g) + O2(g) → 2 NO2(g)
Increasing by 0.021 M⋅min-1
Increasing by 0.042 M⋅min-1
Increasing by 0.084 M⋅min-1
It cannot be determined without knowing the rate law for the reaction.
The rate constant for an elementary chemical reaction can be affected by which of the following?
I. Reactant concentrations
II. Product concentrations
I only
II only
Both I and II
Neither I nor II
Sulfuryl chloride (SO2Cl2) decomposes via first-order kinetics. The half-life is 4.1 minutes at a certain temperature. How long does it take for 30% of the SO2Cl2 in a sample to decompose at this temperature?
0.6 min
2.1 min
2.5 min
7.1 min
The graph below shows the forward and reverse rates for a reaction as a function of time. At time t, a catalyst is added to the system, and the forward reaction rate is observed to change as indicated by the solid curve. Which dashed curve best indicates how the reverse reaction rate changes?
A
B
C
D
The following mechanism is proposed for the oxidation of I– by OCl– in aqueous solution:
OCl– + H2O ↔ HOCl + OH– fast, reversible
HOCl + I– → HOI + Cl– slow
HOI + OH– ↔ OI– + H2O fast, reversible
What reaction orders for OCl–, I–, and OH– are consistent with this mechanism?
A
B
C
D
The endothermic reaction shown below is at equilibrium in a sealed flask, with significant amounts of both Ca(OH)2 (s) and CaO (s) present. Which action will increase the amount of Ca(OH)2 (s) at equilibrium?
Ca(OH)2 (s) ↔ CaO (s) + H2O (g) ∆H° > 0
Crushing the Ca(OH)2 (s) into smaller pieces
Decreasing the temperature of the flask
Adding more CaO(s) to the flask
Adding N2(g) to the flask
A solution of ammonia, NH3, has pH = 11.50. What is the ammonia concentration? (The pKa of NH4+ is 9.24.)
1.7 × 10-5 M
3.2 × 10-3 M
5.5 × 10-3 M
0.58 M
Barium fluoride has Ksp = 1.8 × 10-7. What is the maximum fluoride ion concentration possible in a solution with [Ba2+] = 5.0 × 10-4 M?
3.6 × 10-4 M
3.6 × 10-3 M
9.5 × 10-3 M
1.9 × 10-2 M
A solution containing Co(H2O)62+(aq), CoCl42–(aq), and Cl–(aq) at equilibrium at room temperature is initially pink. When heated, the solution turns blue. Then, when Ag+(aq) is added, the solution turns back to pink. Which statements are correct?
I. Co(H2O)62+(aq) is pink.
II. Formation of CoCl42–(aq) from Co(H2O)62+(aq) and Cl–(aq) is exothermic.
I only
II only
Both I and II
Neither I nor II
What is the average oxidation state of tungsten in sodium phosphotungstate, Na3PW12O40?
+5
+6
+7
-6
Bromate ion and bromide ion react to form bromine in acidic solution. When the reaction is balanced, which statement about H+(aq) is correct?
_H+(aq) + _BrO3–(aq) + _Br–(aq) → _Br2(aq) + _H2O(l)
Its coefficient is twice the coefficient of Br–(aq).
Its coefficient is twice the coefficient of Br2(aq).
Its coefficient is twice the coefficient of BrO3–(aq).
Its coefficient is the sum of the coefficients of BrO3–(aq) and H2O(l).
Which reaction/s is/are spontaneous under standard conditions?
I. 2 Cu+(aq) + Co(s) → Co2+(aq) + 2 Cu(s)
II. 3 Co2+(aq) + 2 In(s) → 2 In3+(aq) + 3 Co(s)
I only
II only
Both I and II
Neither I nor II
An electrolytic cell consists of two copper electrodes immersed in a solution of copper(II) sulfate. What is the result of passing 0.35 A of current through this cell for 1300 s?
The mass of the anode increases by 0.15 g.
The mass of the anode increases by 0.30 g.
The mass of the anode decreases by 0.15 g.
The mass of the anode decreases by 0.30 g.
What is the change in standard free energy at 298 K for the conversion of ozone to molecular oxygen as shown in the equation below?
2 O3(g) → 3 O2(g) ∆G° = ???
–164 kJ⋅mol-1
–328 kJ⋅mol-1
–401 kJ⋅mol-1
–492 kJ⋅mol-1
What is the cell potential of the given galvanic cell (see image) under the stated conditions at 298 K?
+0.884 V
+0.984 V
+1.084 V
+1.120 V
For which element is the +2 oxidation state LEAST common?
Al
V
Fe
Sm
How many completely filled p orbitals are present in a ground state Cl atom?
1
2
4
5
Which atom has the highest first ionization energy?
N
O
P
S
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.
Ga has more protons than Al, so its valence electrons are more attracted to the nucleus.
Ga has a filled 3d subshell, whose electrons incompletely screen the nucleus.
Ga experiences significant relativistic effects, which contract the valence orbitals.
Which set of quantum numbers could NOT correspond to an electron in a ground-state gas phase Pd atom?
n = 2
l = 1
ml = –1
ms = 1/2
n = 3
l = 3
ml = –1
ms = –1/2
n = 4
l = 0
ml = 0
ms = –1/2
n = 4
l = 2
ml = 2
ms = 1/2
A certain nuclide undergoes beta decay to form 70Ge. If the same nuclide undergoes electron capture instead, what daughter nuclide forms?
70Zn
70Ga
70Ge
70As
Which molecule is planar?
CF4
COF2
SF4
SOF2
Which molecule has NO unpaired electrons?
NO
ClO
SO2
ClO2
Phosphorous acid, H3PO3, is a diprotic acid in aqueous solution (pK1 = 2.0, pK2 = 6.6). Which Lewis structure best represents HPO32-?
One Lewis structure of squarate ion, C4O42- , is shown below. Which statement best describes the bond distances in the squarate ion?
All carbon-carbon bond distances are the same, and all carbon-oxygen bond distances are the same.
There are two distinct carbon-carbon bond distances, but all carbon-oxygen bond distances are the same.
There are two distinct carbon-carbon bond distances, and two distinct carbon-oxygen bond distances.
There are three distinct carbon-carbon bond distances, and two distinct carbon-oxygen bond distances.
Which compound is an ester?
A
B
C
D
A pure substance is found to rotate the plane of planepolarized light. Which compound is it?
A
B
C
D
How many distinct compounds have the formula C5H12?
1
2
3
4
5
What is the relationship between the two compounds shown?
Identical
Structural isomers
Geometric isomers
Enantiomers
N-methyl-2-methylpropanamine
N-ethylpropanamine
N-methylbutan-2-amine
2-methylbutan-2-amine
The type of reaction shown is called
Addition Reaction
Elimination Reaction
Free Radical Substitution Reaction
Nucleophilic Substitution Reaction
How much energy is needed to raise the temperature of a 20.0g piece of copper from 15.0 degrees Celsius to 25.0 degrees Celsius? (The specific heat of copper is 0.385 J/g C)
20 x (25-15) = 70 J
20 x 0.385 x (25-15)= 77 J
20 x 0.385 x (15-25) = 62 J
20 x 0.385 x (15-0) = 77 J
When gasoline burns in a car engine, the heat released causes the products CO2 and H20 to expand, which pushes the pistons outward. Excess heat is removed by the car's cooling system. If the expanding gases do 45 1 J of work on the pistons and the system loses 325 J to the surroundings as heat, calculate the change in energy (ΔE) in J.
-776
776
126
-126
