Cell Potential and Free Energy

AP Chemistry· difficulty 4/5

Zn Cu Zn$^{2+}$ Cu$^{2+}$ salt bridge

Calculate EcellE^\circ_{cell} for Zn+Cu2+Zn2++CuZn + Cu^{2+} \rightarrow Zn^{2+} + Cu given E(Zn2+/Zn)=0.76E^\circ(Zn^{2+}/Zn) = -0.76 V and E(Cu2+/Cu)=+0.34E^\circ(Cu^{2+}/Cu) = +0.34 V.

  • A

    Ecell=0.42E^\circ_{cell} = -0.42 V

  • B

    Ecell=1.10E^\circ_{cell} = -1.10 V

  • C

    Ecell=+1.10E^\circ_{cell} = +1.10 V

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  • D

    Ecell=+0.42E^\circ_{cell} = +0.42 V

Explanation

EcellE^\circ_{cell} = EcathodeEanodeE^\circ_{cathode} - E^\circ_{anode} = 0.34 - (0.76-0.76) = +1.10 V. Spontaneous since positive.

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