Chemistry Exam Flashcards
1
Q
- What is the mass of the following isotope Mg-25
A. 25u
B. 24u
C. 24.31 g/mol
D. 24.31u
E. Both C and D are correct
A
Answer: A. 25u
2
Q
- The Lewis structure for hydrogen chloride is shown here. Which type of bond forms between the Hydrogen and Chlorine Atoms
A. Triple covalent bond
B. Single polar covalent bond
C. Double non-polar covalent bond
D. Single polar ionic bond
E. Single non-polar covalent bond
A
Answer: B. Single polar covalent bond
3
Q
- Which term describes an upper medium strong attractive force between two polar molecules?
A. Hydrogen bond
B. Dipole-dipole force
C. London dispersion force’
D. Polar covalent bond
E. Any of the above
A
Answer: A. Hydrogen bond
4
Q
- Which of the following is an example of a non-polar molecule?
A. H2O
B. CO
C. NH3
D. H2CO
E. CO2
A
Answer: E. CO2 (has a linear molecular geometry with the two polar C-O bonds pointing in opposite directions. As a result, the individual bond dipoles cancel out, making CO2 a non-polar molecule)
5
Q
- Which of the following will dissolve in polar solvents such as water?
A. Non-polar solvents with ionic compounds
B. Ionic compounds and polar covalent compounds
C. Non-polar solvents and non-polar compounds
D. Both A and C
E. All of the above
A
Answer: B. Ionic compounds and polar covalent compounds
6
Q
- What is true of a polar solid?
A. It has polar covalent bonds with an electronegativity difference of 0.5 to 1.7
B. It will dissolve in water but not conduct electricity when dissolved
C. Both A and B are true
D. It has full charges
E. None of the above are true
A
Answer: C. Both A and B are true
7
Q
- Which of the following elements has the largest atomic radius?
A. Magnesium
B. Sodium
C. Sulphur
D. Chlorine
E. Silicon
A
Answer: B. Sodium (As you move from right to left across a period (horizontal row) in the periodic table, the atomic radius generally increases. This is because there are fewer protons pulling the electrons towards the nucleus, resulting in a larger atomic radius.)
8
Q
- Which of the following elements has the highest electronegativity?
A. Magnesium
B. Oxygen
C. Nitrogen
D. Chlorine
E. Fluorine
A
Answer: E. Fluorine (top right)
9
Q
- What is the molecular shape of water as determined by VSEPR theory?
A. Tetrahedral
B. Trigonal planar
C. Bent or Angular
D. Linear
E. None of the above
A
Answer: B. Trigonal planar
10
Q
- Look at the molecule on the right. What is missing in the diagram for NCl3? (Note N-Cl bonds have an electronegativity difference of only 0.2).
A. Partial Charges
B. Dipoles
C. Electrons around the Cl atoms
D. Another Cl atom, most of the time N makes 4 bonds
E. Electrons on the N
A
Answer: C. Electrons around the Cl atoms
11
Q
- In the equation of a precipitation reaction, which state symbol indicates an ion in solution?
A. (l)
B. (s)
C. (g)
D. (sl)
E. (aq)
A
Answer: E. (aq) (is the state symbol that indicates an ion in solution, Aqueous solutions are formed when ionic compounds dissociate into their constituent ions in water.)
12
Q
- Which type of reaction does this illustration represent?
A. Decomposition reaction
B. Double displacement reaction
C. Synthesis reaction
D. Single displacement reaction
E. Acid-base neutralization
A
Answer: D. Single displacement reaction
13
Q
- Which of the following shows a balanced chemical equation for the decomposition of potassium chlorate, KClO3, into potassium chloride and oxygen?
A. 2KClO3(S) = 2KCI(s) + 2O2(g)
B. 2KClO3(S) = 1KCI(s) + 3O2(g)
C. 1KClO3(S) = 2KCI(s) + 3O2(g)
D. 2KClO3(S) = 2KCI(s) + 3O2(g)
E. 2KClO3(S) = 2KCI(s) + 1O2(g)
A
Answer: D. 2KClO3(S) = 2KCI(s) + 3O2(g)
14
Q
- How would you know that the reaction from #13 above is a decomposition reaction
A. Only one reactant is seen and only 1 product is seen
B. Only one reactant is seen and more than one product is seen
C. The mole ratio between KClO3 and O2 is not even
D. Only one product is seen and it came from more than 1 reactant
E. A solid and a gas are produced
A
Answer: B. Only one reactant is seen and more than one product is seen
15
Q
- What are the products of the complete combustion of propane?
A. CO2 and H2O
B. CO3 and H2O
C. CO and H2
D. C, O2 and H2
E. CO2, CO, C, and H20
A
Answer: A. CO2 and H2O
16
Q
- Which statement is true about the activity series of metals?
A. The Solid metal must be below the Solution metal for displacement to occur
B. The Solid metal must be above the Solution metal for displacement to occur
C. The further apart the two elements are the slower the displacement reaction
D. The closer the elements are to each other the faster the displacement reaction
E. None of the elements can displace any others.
A
Answer: B. The Solid metal must be above the Solution metal for displacement to occur
17
Q
- Why can Vinegar (acetic acid) be used to clean tarnished silverware but not rusted iron on the side of a car? Acids are a source of Hydrogen ions.
A. H from Acid only reacts with Iron and no other metals
B. Silver is higher than H on the activity series while Iron is below H
C. Silver is lower than H on the activity series while Iron is above H
D. Iron (III) Oxide (rust) is very reactive to acid.
E. Vinegar is actually not a good cleaner and shouldn’t be used on silver
A
Answer: C. Silver is lower than H on the activity series while Iron is above H
18
Q
- Why should the flame in your furnace at home be blue instead of yellow?
A. Blue flames indicate complete burning producing little to no CO gas
B. Yellow flames indicate incomplete burning producing lots of CO gas
C. Both A. and B.
D. CO gas is super corrosive and flammable
E. Both A. and D.
A
Answer: C. Both A. and B.
19
Q
- Why is CaCl2(s) an effective material for road salt to melt ice while AgCl(s) is not?
A. CaCl2(s) can dissolve in ice to melt it while AgCI(s) cannot dissolve well in ice
B. Ca is cheaper than Ag making road salt easier to buy
C. Ca is a useful nutrient while Ag is not
D. Ca is an alkaline metal and basic metals are better at dissolving than other metals
E. Ca produces hydrogen gas in water which is flammable creating heat
A
Answer: A. CaCl2(s) can dissolve in ice to melt it while AgCI(s) cannot dissolve well in ice
20
Q
- Why is FeCO3(s) a solid?
A. Iron Carbonate is an ionic compound
B. Carbonates are usually aqueous but Fe is an exception
C. Fe compounds are always solid no exceptions
D. Carbonates are always solids no exceptions
E. Carbonates are usually solids and Fe is not an exception
A
Answer: E. Carbonates are usually solids and Fe is not an exception
21
Q
- Iron metal is extracted from Magnetic ore according to the following reaction
1Fe3O4(s) + 2C(s) = 3Fe(s) + 2CO2(g)
What does the mole ratio of C/Fe mean?
A. For every 2 moles of C used 3 moles of Fe are produced
B. For every 2 moles of Fe produced 3 moles of C are used
C. For every 1 mole of Fe3O4 used 3 moles of Fe are produced
D. For every 3 moles of Fe that are used 2 moles of C are produced
E. Nothing, the mole ratio is not useful in evaluating the chemical reactions
A
Answer: A. For every 2 moles of C used 3 moles of Fe are produced
22
Q
- In the Magnetic reaction above, if 12 moles of C(s) are used, how many moles of Fe(s) are produced?
A. 18
B. 12
C. 9
D. 6
E. 3
A
Answer: A. 18
23
Q
- What is the molar mass of Sodium Phospite Na3PO3?
A. 101.96 g/mol
B. 147.94 g/mol
C. 148.94 g/mol
D. 69.96 g/mol
E. 115.94 g/mol
A
Answer: B. 147.94 g/mol
24
Q
- If 1.89 g of a 5.00 g sample of an organic compound is carbon. What is the percentage of carbon in this compound?
A. 15.6%
B. 0.387%
C. 0.378
D. 37.8%
E. 0.156%
A
Answer: D. 37.8%
25
25. Which of the following is Avogadro’s constant?
A. 1.02 x 10^22
B. 6.02 x 10^29
C. 6.02
D. 3.01 x 10^23
E. 6.02 x10^23
Answer: E. 6.02 x10^23
26
26. What is the total number of molecules present in 3.00 mol of CaCl2
A. 3.61 × 10^24
B. 1.81 x 10^24
C. 3
D. 1.20 x 10^24
E. 6.02 x 10^23
Answer: B. 1.81 x 10^24
27
27. Which of the following is an Empirical Formula?
A. C2H2
B. C3H3
C. C1H1
D. C2H4O2
E. C4H8O4
Answer: C. C1H1
28
28. If the Empirical formula for a substance is C1H2O1 and the Molecular formula has a Molar Mass of 180.18g/mol, what is the molecular formula?
A. C6H12C6
B. C2H4O2
C. C4H8O4
D. C1H2O1
E. C0.17H0.34O0.17
Answer: A. C6H12C6
29
29. If 3 mol of Calcium metal are reacted with 10 moles of H3PO4. Which substance is the Limiting Reagent?
The reaction is:
3Ca(s) + 2H3PO4 = 1Ca3(PO4)2 + 3H2(g)
A. H3PO4
B. Ca
C. Ca3(PO4)2
D. H2
E. None of the above
Answer: Ca
30
30. The reaction in Q#29 can be used to make H2(g). If the Theoretical yield of H2(g) is 22 g and the actual yield is 18.5g, what is the % yield?
A. 100%
B. 0.84%
C. 119%
D. 1.19%
E. 84%
Answer: E. 84%
31
31. In making a solution, which substance is the solvent?
A. The substance that is dissolved
B. Always a gas
C. The solid powder
D. The substance that does the dissolving
E. Any of the above
Answer: D. The substance that does the dissolving
32
32. What is the definition of Molar Concentration?
A. The moles of a substance dissolved in 1 L of solution
B. The mass of a substance dissolved in a solution
C. The number of particles of a substance dissolved in a solution
D. The Volume of solvent used to dissolve the solute
E. How well someone pays attention during a lesson on Moles
Answer: A. The moles of a substance dissolved in 1 L of solution
33
33. Which term describes the process of reducing the concentration of a solution by adding more solvent?
A. Dissociation
B. Transpiration
C. Hydration
D. Dilution
E. Reduction
Answer: D. Dilution
34
34. How many moles are contained in 0.250 L of 0.500 Mol/L NaCl?
A. 2 mol
B. 0.125 mol
C. 0.15 mol
D. 12.5 mol
E. 125 mol
Answer: B. 0.125 mol
35
35. Copper (II) Sulfate solutions start out blue. How would the appearance of the diluted solution compare to the original solution?
A. The diluted solution would be more of a green colour
B. The diluted solution would be completely colourless
C. The diluted solution would be a darker blue
D. The diluted solution would be a lighter blue
E. There would be no change in the appearance
Answer: D. The diluted solution would be a lighter blue
36
36. What volume of a 4.00mol/L H2SO4 solution is required to make 300 ml of a 0.500 mol/L solution?
A. 0.00375 L
B. 0.0375 L
C. 037.5 L
D. 3.75 L
E. 0.375 L
Answer: B. 0.0375 L (in C1V1 = C2V2, solve for V1)
37
37. Someone once said “The solution to Pollution is Dillution”. Is this true? Why?
A. Yes because the concentration is more spread out
B. No because the same amount of chemical is still there it is just mixed in with more water
C. Yes because water cleans everything
D. No because adding more water means you need to add more chemicals
E. Yes because water is the cheapest way to deal with chemicals
Answer: A. Yes because the concentration is more spread out
38
38. There was a spill of Barium Nitrate in a rural area where people use well water as their drinking water. Which chemical (NaCl or Na2SO4) would be best to add the spill to remove the Ba from the water supply?
A. Na2SO4 since Barium Sulfate (BaSO4) does not dissolve in water
B. NaCl since Ba is insoluble when mixed with Na
C. NaCl since BaCl2 does not dissolve in water
D. Neither since Barium is soluble with both Chloride (CI^-1) and Sulfate (SO4^-2)
E. Both could be used since both BaCl2 and BaSO are insoluble in water
Answer: A. Na2SO4 since Barium Sulfate (BaSO4) does not dissolve in water
39
39. What is a Strong Acid?
A. An acid that ionizes 100%, releasing OH-1 ions
B. An acid that only partially ionizes releasing H+1 ions
C. An acid that completely ionizes releasing H+1 ions giving a low pH
D. An acid that completely ionizes releasing H+1 ions giving a high ph
E. An acid that completely ionizes releasing H+1 ions giving a medium ph
Answer: C. An acid that completely ionizes releasing H+1 ions giving a low pH
40
40. What is the pH of a solution of HCI (Hydrochloric acid with an H+1 concentration of 4.5x10^-4?
A. 3.64
B. -3.35
C. 4.5
D. -4.5
E. 3.35
Answer: E. 3.35
41
41. Bromine has 2 isotopes, Bromine-10 with a natural abundance of 19.8% and Bromine-11 with a natural abundance of 80.2%. Use this to determine the average atomic mass of Bromine
Givens:
%Br-10a = 19.8%
%Br-11b = 80.2%
Required
Average atomic mass =?
Analysis
Average atomic mass = %a(Ma)/100 + %b(Mb)/100
= 19.8%(10)/100 + 80.2%(11)/100
= 1.98u + 8.822u
Solution
= 10.802u
Phrase
Therefore the average atomic mass of Bromine is 10.802u.
42
Name of NO2
Nitrogen Dioxide
43
Name of Ni(ClO3)2
Nickel (II) Chlorate
44
Name of HI(aq)
Hydroiodic Acid
45
Formula of Barium Hydroxide
Ba(OH)2
46
Formula of Zinc Chloride Heptahydrate
ZnCl2 * 7H20
47
Formula of Silicon tetrabromide
SiBr4
48
Balance
a) ? Sr(s) + ? H2O(l) = ? Sr(OH)2(s) + ? H2(g)
a) 1 Sr(s) + 2 H2O(l) = 1 Sr(OH)2(s) + 1 H2(g)
49
Balance
c) ? Al(s) + ? Cu3(PO4)2(aq) = ? AlPO4(aq) + ? Cu(s)
c) 2 Al(s) + 1 Cu3(PO4)2(aq) = 2 AlPO4(aq) + 3 Cu(s)
50
Products and Reaction Type
CH4(g) + O2(g) =
CH4(g) + O2(g) = H2O + CO2
Complete Combustion
51
Products and Reaction Type
Na(s) + Cl2(g) =
Na(s) + Cl2(g) = NaCl
Synthesis
52
Products and Reaction Type
Cu(s) + MgCl2(aq) =
Cu(s) + MgCl2(aq) = no reaction
Single Displacement
53
Products and Reaction Type
K3PO4(aq) + Ni(NO3)3(aq) =
K3PO4(aq) + Ni(NO3)3(aq) = Ni(PO4)(s) + K(NO3)(aq)
Double Displacement
54
45. Ammonia (NH3) reacts with Oxygen gas to produce Nitrogen monoxide NO(g) + water according to the equation:
If 5g of NH3 reacts with more than enough oxygen, how many grams of H2O are formed?
4NH3(g) + 5O2(g) = 4NO(g) + 6H2O(g)
4NH3(g) + 5O2(g) = 4NO(g) + 6H2O(g)
m 5.00g In Excess N/A z = ?
MM 17.04g/mol 18.02g/mol
n x = ? y = ?
Step 1: Find the molar mass of NH3 and H2O
MM = 1(m-nitrogen) + 3(m-hydrogen)
MM = 1(14.01g) + 3(1.01g)
MM = 17.04g/mol
MM =2(m-hydrogen) + 1(m-o)
MM = 2(1.01g) + 1(16.00g)
MM = 18.02g/mol
Step 2: Find the moles of NH3 using n=m/mm
n = m/MM
n = 5g/17.04g/mol
n = 0.2934mol
Therefore there are 0.2934moles in NH3
Step 3: Find the moles of H2O using the mole ratio
NH3/H2O = 4/6 = 0.2934mol/x
4x = 6(0.2934mol)
4x = 1.7604
x = 1.7604/4
x = 0.4401mol
Therefore there are 0.4401 moles in H2O.
Step 4: Find the mass of H2O using m = n(MM)
m = n(MM)
m = 0.4401mol(18.02g/mol)
m = 7.93g
Therefore there are 7.93 grams of H2O(g) are formed.
55
46. In the following reaction, Iron solid, Fe(s), reacts with Chlorine gas, Cl2(g), to make Iron 8 Chloride, FeCl3(s). If 30g of Fe(s) reacts with 10g of Cl2(g), which reactant is the limiting reagent?
2Fe(s) + 3Cl2 = 2FeCl3(g)
2Fe(s) + 3Cl2 = 2FeCl3(g)
m 30g 10g n/a
MM 55.85 g/mol 70.9g/mol
n x = ? y = ?
Step 1: Calculate the moles of Fe using n=m/MM
n = m/MM
n = 30g/55.85g/mol
n = 0.537 moles
Therefore there are 0.537 moles in Fe
Step 2: Calculate the moles of Cl using n=m/MM
n = m/MM
n = 10g/70.9g/mol
n = 0.141mol
Therefore there are 0.141 moles in Cl
Step 3: Use the mole ratio to see how much Cl you SHOULD get
Fe/Cl = ⅔ = 0.537mol/x
2x = 3(0.537mol)
2x = 1.611
x = 1.611/2
x = 0.8055mol
Therefore, as we only have 0.141 mol of Cl and we need 0.8055mol, Cl is the limiting reagent.
56
47.
a) What type of compound is KNO3 and what type of compound is K2SO4 (covalent, polar covalent, or Ionic)? How do you know?
They’re both ionic as they are both metals bonded with nonmetals, creating Ionic salts.
57
b) What type of molecule is water?
**** delta negative so -
O
^ / \ ^
H H
delta positive on both H is so +
Overall dipole arrow up
O 3.4
H -2.2
= 1.2 polar-covalent, partial charges
O 3.4
H -2.2
= 1.2 polar-covalent, partial charges
Therefore the overall polarity of water is polar
58
c) Will the fertilizers be able to dissolve?
Ionic KNO3 and K2SO4 have full charges that are attracted to the partial charges in polar water. Therefore the KNO3 and K2SO4 molecules will mix with the water molecules and dissolve.
59
d) The molar mass of KNO3 is 101.11g/mol and the molar mass of K2SO4 is 174.27g/mol. What is the %comp of potassium in each fertilizer? What is a better source of potassium?
Givens
MM-K = 39.1g/mol
MM-KNO3 = 101.11g/mol
MM-K2SO4 = 174.27g/mol
Required
%composition of K = ?
Analysis
%comp = K/NO3 x 100
= 39.1g/mol/101.11g/mol x 100
Solution = 38.67%
%comp = 2(MM of K)/K2SO4 x 100
= 2(39.1g/mol)/174.27g/mol x100
Solution %comp = 44.87%
Phrase
Therefore K2SO4 is a better source of potassium
60
e) If the farmer has 8mol of fertilizer and a container that can hold 14000L of water, what concentration of fertilizer can the farmer make?
Givens
n = 8mol
v = 14000L
Required
c = ?
Analysis
c = n/v
c = 8mol/14000L
c = 0.00057mol/L
Phrase
He can make a 0.00057mol/L concentration
61
48. Vinegar titration:
2CH3COOH + 1 Ca(OH2) = 1Ca(CH3COO)2(aq) + 2H2O
a) 40ml of 0.230mol/L Ca(OH)2 is needed to titrate 12ml of the vinegar solution. Write the knowns and unknowns for the two reactants under the balanced equation above.
2CH3COOH + 1 Ca(OH2) = 1Ca(CH3COO)2(aq) + 2H2O
C z =? 0.230mol/L
V 0.012L 0.04L
N y=? x = ?
62
b) What’s the concentration of the vinegar?
Step 1: Find moles in Ca(OH2) using n=cv
n = cv
n = (0.230mol/L)(0.04L)
n = 0.0093
Therefore there are 0.0092 moles in Ca(OH2)
Step 2: Find moles in Ca(OH2) using the mole ratio
CH3COOH/Ca(OH2) = 2/1 = x/0.0092mol
1x = 2(0.0092mol)
1x = 0.0184mol
x = 0.0184mol/1
x = 0.0184mol
Therefore there are 0.0184 moles in Ca(OH2).
Step 3: Find C using C = N/V
c = n/v
c = 0.0184mol/0.012L
c = 1.53 mol/L
Therefore the concentration of vinegar is 1.53mol/L.
63
c) Is the vinegar solution a proper 5% (0.83mol/L) or does it need to be diluted? How do you know?
It does need to be diluted because the concentration is more than 0.83 mol/L.
