NET, IAS, State-SET (KSET, WBSET, MPSET, etc.), GATE, CUET, Olympiads etc.: Chemistry MCQs (Practice_Test 10 of 31)
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- In recitation, you studied the electrochemistry involved in the “fruit clock” If an orange is used to power the fruit clock, which of the following statements is TRUE?
- Free electrons flow through the orange to maintain electrical neutrality.
- The orange allows the Zn2 + and Cu2 + ions produced in the reaction to mix thereby maintaining electrical neutrality.
- The orange functions as the anode.
- The orange functions as the salt bridge by maintaining electrical neutrality.
- The acids present in the orange are oxidized at the anode to produce hydrogen gas.
- Which of the following reactions IS a reduction-oxidation reaction?
- formation of N2 in automobile airbags: 2NaN3 (s) ⇾ 2Na (l) + 3N2 (g)
- combustion of propane in a gas grill: C3H8 (g) + 5O2 (g) ⇾ 3CO2 (g) + 4H2O (g)
- decomposition of hydrogen peroxide (H2O2) by light: 2H2O2 (aq) ⇾ 2H2O (l) + O2 (g)
- All of these are reduction-oxidation reactions.
- None of these are reduction-oxidation reactions.
- Which of the following metals could be used successfully to galvanize iron?
- Ni
- Cu
- Sn
- Co
- Mn
- Calculate the standard cell potential (in V) for the following reaction at 25oC. 2Cr (s) + 3Ni2 + (aq) ⇾ 2Cr3 + (aq) + 3Ni (s)
- The layer of zinc on a piece of galvanized iron can be removed by placing it in a concentrated solution of acid. Calculate the standard cell potential (in V) for this reaction.
- A beaker contains a small amount of gold dust (Au (s) ) . Which of the following aqueous solutions, when added to the beaker, would dissolve the gold dust (i.e. … convert Au (s) to Au3 + (aq) ) ?
- Cr2O72- (acidic solution)
- H2O2 (acidic solution)
- Br2
- Zn2 +
- Al3 +
- Which of the following statements best describes what will happen when liquid bromine (Br2) is poured into a beaker containing aluminum metal?
- Br2 will be reduced; Al will be oxidized
- Br2 will be oxidized; Al will be reduced
- Br2 will function as the reducing agent; Al will function as the oxidizing agent
- A reaction will not occur.
- It is impossible to tell.
- Consider the following galvanic cell reaction at 25oC, 4Cr2 + (aq) + O2 (g) + 4H3O + (aq) ⇾ 4Cr3 + (aq) + 6H2O (l) Which of the following statements best describes what would happen to the cell potential if the concentration of Cr2 + is increased?
- The cell potential would become less positive.
- The cell potential would become more positive.
- The cell potential would remain the same.
- It is impossible to tell.
- Which of the following half-reactions is involved in the STANDARD HYDROGEN ELECTRODE?
- Pt2 + (aq) + 2e________ > Pt (s)
- 2H3O + (aq) + 2e________ > 2H2O (l) + H2 (g)
- H2O2 (aq) + 2H3O + (aq) + 2e________ > 4H2O (l)
- O2 (g) + 2H2O (l) + 4e________ > 4OH- (aq)
- None of the above:
- A concentration cell containing aqueous solutions of Cu (NO3) 2 and solid copper metal is constructed so that the Cu2 + ion concentration in the cathode half-cell is 0.66 M. Calculate the concentration of the Cu2 + ion in the anode half-cell if the cell potential for the concentration cell at 25oC is 0.034 V.
- Consider a galvanic cell based on the following overall reaction, Fe (s) + 2Ag + (aq) ⇾ Fe2 + (aq) + 2Ag (s) Calculate the cell potential (in V) for this reaction at 25oC when the concentration of Ag + ions is 0.050 M and the concentration of Fe2 + ions is 1.50 M.
- Which of the following metal ions will plate out on a piece of galvanized iron which has NOT had the layer of Zn metal removed?
- Cu2 +
- Au3 +
- Ni2 +
- All of these.
- None of these.
- Which of the following best explains why concentration cells must be run under non-standard conditions in order for them to do electrical work?
- A concentration cell can only do electrical work when either NH3 or NaOH is added to one of the half-cells.
- A concentration cell cannot do electrical work at 25oC.
- The change in free energy for a concentration cell is always negative under standard conditions.
- A concentration cell has a cell potential equal to zero under standard conditions.
- A concentration cell can only do electrical work when the cell is run under standard conditions.
- Which of the following statements about a salt bridge in a voltaic cell is TRUE?
- Free electrons flow through the salt bridge to maintain electrical neutrality in the two half-cells.
- The salt bridge allows the ions present in the two half-cells to mix extensively.
- The wire must be connected directly to the salt bridge in order for the salt bridge to be able to maintain electrical neutrality in the two half-cells.
- In some cases, a salt bridge functions as the anode.
- Ions from the electrolyte in the salt bridge flow into each half-cell to maintain electrical neutrality.
- Which of the following reactions can be used to construct a voltaic cell?
- H3O + (aq) + OH- (aq) ⟺ 2H2O (l)
- HF (g) + H2O (l) ⟺ H3O + (aq) + F- (aq)
- Cu2 + (aq) + 4F- (aq) ⟺ CuF42- (aq)
- O2 (g) + 4H3O + (aq) + 4I- (aq) ⟺ 2I2 (aq) + 6H2O (l)
- 2NO2 (g, nitrogen dioxide) ⟺ N2O4 (g, dinitrogen tetroxide)