Test tasks

 

 

1. Oxidation is defined as …
A. gain of a proton
B. loss of a proton
C. gain of an electron
D. loss of an electron
E. capture of an electron by a neutron
2. What is the oxidation number of each boron atom in the compound, Na2B4O7?
A. -3
B. +1
C. +5
D. +6
E. +3
3. When you balance the equation for the redox reaction below,
C4H10(l) + Cr2O72-(aq) + H+(aq) → H6C4O4(s) + Cr3+(aq) + H2O(l)
the oxidizing agent is
A. C4H10(l)
B. H+(aq)
C. Cr2O72-(aq)
D. H6C4O4(s)
E. Cr3+
4. In a chemical reaction, magnesium metal reacts with aqueous sulfuric acid solution to produce mag-nesium sulfate (in solution) and hydrogen gas. In the course of the reaction, which element under-goes an increase in oxidation number?
A. hydrogen, only
B. magnesium, only
C. oxygen, only
D. sulfur, only
E. magnesium and hydrogen
5. In terms of activity, the series in increasing order for metals is found to be,
Au < Ag < Cu < Sn < Cd < Zn < Al < Mg < Na < Cs
Based on this list, which one of the elements presented below would undergo oxidation most readily?
A. Ag
B. Al
C. Cu
D. Cd
E. Zn
6. What is the oxidation number of the chlorine atom in the HClO4 molecule?
A. -1
B. +3
C. +5
D. +7
E. +9
7. Iron in a sample with non-interfering substances can be determined by a titration using dichromate ion in acidic solution. The iron is converted to Fe2+ (aq) ions which are then titrated by the dichromate ion. The reaction is:
6 Fe2+(aq) + Cr2O72-(aq) + … → 6 Fe3+(aq) + … Cr3+(aq) + …
How many grams of iron are there present in a sample if it required 42.7 ml of 0.0180 molar Na2Cr2O7 (aq) solution for the titration described by the incomplete equation above?
A. 0.043 g
B. 3.61 g
C. 7.07 g
D. 7.15 g
E. 0.258 g
8. Which one of the following processes represents a reduction?
A. CrO42- → Cr3+
B. Ba2+ + CrO42- → BaCrO4
C. MnO2 → MnO4-
D. 2H+ CO32- → H2O + CO2
E. 2CrO42- + 2H+ → Cr2O7 + H2O
9. What is the change in oxidation number of each chromium atom in the process,
K2Cr2O7 → Cr2(SO4)3
A. -1
B. -6
C. +3
D. -3
E. +6
10. What is the oxidation number of the potassium atom in the compound, K2O?
A, -1
B. -1
C. +2
D. +4
E. +1
11. Balance the half reaction, Cl2O7 (g) → HClO (aq), taking place in acidic media. Which answer below describes how many electrons are needed to balance the half reaction?
A. 2 electrons, left side
B. 3 electrons, right side
C. 12 electrons, left side
D. 6 electrons, right side
E. 8 electrons, left side
12. In a series of chemical test reactions the following observations were made when some metallic element samples were treated with 3.00 molar hydrochloric acid solution. Zn: metal dissolves, hydrogen gas is emitted. Cu: no reaction. Ag: no reaction. Mg: metal dissolves, hydrogen gas is emitted. Mn: metal dissolves, hydrogen gas is emitted. Which statement below is true?
A. Mg, Mn, Zn are more reactive than Ag, Cu; but less reactive than H2.
B. Mg, Mn, Zn are less reactive than Ag, Cu; but more reactive than H2.
C. Mg, Mn, Zn are more reactive than Ag, Cu; and more reactive than H2.
D. Mg, Mn, Zn are less reactive than Ag, Cu; and less reactive than H2.
E. These observations are insufficient to form any judgment about relative reactivity of any of the elements listed above.
13. What is the oxidation number of each oxygen atom in the compound, BaO2?
A. -1
B. -2
C. +1
D. +2
E. +3
14. … is a chemical reaction in which the atoms or ions of an element acquire a more positive oxidation state by losing electrons.
A. Reduction
B. Oxidation
C. Oxidation number
D. Reducing agent
E. No right answer
15. What is the oxidation number of the chlorine atom in the HClO4 molecule?
A. -1
B. +3
C. +5
D. +7
E. +9
16. Which one of the following processes represents an oxidation?
A. Ba2+ + CrO42- → BaCrO4
B. 2H+ + CO32- → H2O + CO2
C. Fe3+ → Fe2+
D. MnO2 → MnO4-
E. 2CrO42- + 2H+ → Cr2O72- + H2O
17. Which one of the statements below is true concerning an oxidation-reduction reaction?
A. the reactant which is being reduced is the reducing reagent
B. the reactant which is being oxidized is the reducing reagent
C. the reactant which gains electrons is the reducing reagent
D. the reactant which loses electrons is the oxidizing reagent
E. none of the statements, a—d, is true for an oxidation-reduction reaction
18. Balance the half reaction, C5O52- (g) → CO32- (aq), taking place in basic media. Which answer below describes how many electrons are needed to balance the half reaction?
A. 8 ions, left side
B. 12 ions, right side
C. 12 ions, left side
D. 20 ions, right side
E. 20 ions, left side
19. … is a chemical reaction in which the atoms or ions of an element acquire a more negative oxidation state by gaining electrons.
A. Reduction
B. Oxidation
C. Oxidation number
D. Reducing agent
E. No right answer
20. What are the oxidation numbers in hydrogen peroxide, H2O2?
A. 0
B. +1; -1
C. +1
D. -1
E. +2