In Fe(s) | Fe²⁺(aq) || Cu²⁺(aq) | Cu(s), what do (s) and (aq) show?Answer: The phase of each species: solid, or dissolved in water. Source: LibreTexts Chemistry, Electrochemistry, Voltaic Cells: Cell Diagrams (cell notation rules). Read 2026-10-03.
In the cell Cd(s) | Cd²⁺(aq) || Ag⁺(aq) | Ag(s), which electrode is the cathode?Answer: Ag(s). Source: LibreTexts Chemistry, Electrochemistry, Voltaic Cells: Cell Diagrams (cell notation rules). Read 2026-10-03.
In the cell Cu(s) | Cu²⁺(aq) || Ag⁺(aq) | Ag(s), which species is reduced?Answer: Ag⁺(aq). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
In the cell Mg(s) | Mg²⁺(aq) || Ag⁺(aq) | Ag(s), which species is oxidized?Answer: Mg(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
In the cell Ni(s) | Ni²⁺(aq) || Ag⁺(aq) | Ag(s), where does reduction take place?Answer: At Ag(s), the cathode, on the right. Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
In the cell Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s), which electrode is the anode?Answer: Zn(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
Show all 34 questions (28 more)
Read it, continued
In Zn(s) | Zn²⁺(aq, 1.0 M) || Cu²⁺(aq, 1.0 M) | Cu(s), what does 1.0 M tell you?Answer: The concentration of that ion in its solution. Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
One beaker holds a cadmium electrode in Cd(NO₃)₂ solution, the other a silver electrode in AgNO₃ solution. Why is NO₃⁻ missing from Cd(s) | Cd²⁺(aq) || Ag⁺(aq) | Ag(s)?Answer: Spectator ions are left out. Source: LibreTexts Chemistry, Electrochemistry, Voltaic Cells: Cell Diagrams (cell notation rules). Read 2026-10-03.
Reading a line of cell notation from left to right follows the path of what?Answer: The electrons, anode to cathode. Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
What does a single vertical line stand for in cell notation?Answer: A boundary between two phases, such as a solid electrode and a solution. Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
What does the double vertical line stand for in cell notation?Answer: The salt bridge, or other junction, between the two half-cells. Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
Which half-cell is written on the left in a line of cell notation?Answer: The anode, where oxidation happens. Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
Which overall reaction does Zn(s) | Zn²⁺(aq) || Ag⁺(aq) | Ag(s) stand for?Answer: Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
Within one half-cell, in which order are the species written?Answer: The reactant first, then the product. Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
Write it 10
A galvanic cell runs on 2Al(s) + 3Cu²⁺(aq) → 2Al³⁺(aq) + 3Cu(s). Which line is its cell notation?Answer: Al(s) | Al³⁺(aq) || Cu²⁺(aq) | Cu(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
A galvanic cell runs on 2Al(s) + 3Zn²⁺(aq) → 2Al³⁺(aq) + 3Zn(s). Which line is its cell notation?Answer: Al(s) | Al³⁺(aq) || Zn²⁺(aq) | Zn(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
A galvanic cell runs on Fe(s) + 2Ag⁺(aq) → Fe²⁺(aq) + 2Ag(s). Which line is its cell notation?Answer: Fe(s) | Fe²⁺(aq) || Ag⁺(aq) | Ag(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
A galvanic cell runs on Mg(s) + Cu²⁺(aq) → Mg²⁺(aq) + Cu(s). Which line is its cell notation?Answer: Mg(s) | Mg²⁺(aq) || Cu²⁺(aq) | Cu(s). Source: LibreTexts Chemistry, Electrochemistry, Voltaic Cells: Cell Diagrams (cell notation rules). Read 2026-10-03.
A galvanic cell runs on Ni(s) + 2Ag⁺(aq) → Ni²⁺(aq) + 2Ag(s). Which line is its cell notation?Answer: Ni(s) | Ni²⁺(aq) || Ag⁺(aq) | Ag(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
A galvanic cell runs on Ni(s) + Cu²⁺(aq) → Ni²⁺(aq) + Cu(s). Which line is its cell notation?Answer: Ni(s) | Ni²⁺(aq) || Cu²⁺(aq) | Cu(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
A galvanic cell runs on Pb(s) + Cu²⁺(aq) → Pb²⁺(aq) + Cu(s). Which line is its cell notation?Answer: Pb(s) | Pb²⁺(aq) || Cu²⁺(aq) | Cu(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
A galvanic cell runs on Sn(s) + 2Ag⁺(aq) → Sn²⁺(aq) + 2Ag(s). Which line is its cell notation?Answer: Sn(s) | Sn²⁺(aq) || Ag⁺(aq) | Ag(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
A galvanic cell runs on Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s). Which line is its cell notation?Answer: Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
A galvanic cell runs on Zn(s) + Ni²⁺(aq) → Zn²⁺(aq) + Ni(s). Which line is its cell notation?Answer: Zn(s) | Zn²⁺(aq) || Ni²⁺(aq) | Ni(s). Source: Purdue University, General Chemistry Topic Review, Electrochemical Cells: Line Notation for Voltaic Cells. Read 2026-10-03.
Inert electrodes and gases 10
A galvanic cell runs on Fe(s) + 2H⁺(aq) → Fe²⁺(aq) + H₂(g). Its hydrogen half-cell is a platinum wire in acid with H₂ gas at the surface. Which line is its cell notation?Answer: Fe(s) | Fe²⁺(aq) || H⁺(aq) | H₂(g) | Pt(s). Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
A galvanic cell runs on H₂(g) + 2Ag⁺(aq) → 2H⁺(aq) + 2Ag(s). Its hydrogen half-cell is a platinum wire in acid with H₂ gas at the surface. Which line is its cell notation?Answer: Pt(s) | H₂(g) | H⁺(aq) || Ag⁺(aq) | Ag(s). Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
A galvanic cell runs on H₂(g) + Cu²⁺(aq) → 2H⁺(aq) + Cu(s). Its hydrogen half-cell is a platinum wire in acid with H₂ gas at the surface. Which line is its cell notation?Answer: Pt(s) | H₂(g) | H⁺(aq) || Cu²⁺(aq) | Cu(s). Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
A galvanic cell runs on Mg(s) + 2H⁺(aq) → Mg²⁺(aq) + H₂(g). Its hydrogen half-cell is a platinum wire in acid with H₂ gas at the surface. Which line is its cell notation?Answer: Mg(s) | Mg²⁺(aq) || H⁺(aq) | H₂(g) | Pt(s). Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
A galvanic cell runs on Zn(s) + 2H⁺(aq) → Zn²⁺(aq) + H₂(g). Its hydrogen half-cell is a platinum wire in acid with H₂ gas at the surface. Which line is its cell notation?Answer: Zn(s) | Zn²⁺(aq) || H⁺(aq) | H₂(g) | Pt(s). Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
In the cell Pt(s) | H₂(g) | H⁺(aq) || Ag⁺(aq) | Ag(s), which species is oxidized?Answer: H₂(g). Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
In the cell Zn(s) | Zn²⁺(aq) || H⁺(aq) | H₂(g) | Pt(s), what is formed at the cathode?Answer: H₂(g). Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
Where is an inert electrode such as platinum written in a line of cell notation?Answer: At the outer end of its own half-cell. Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
Why does the half-cell Pt(s) | H₂(g) | H⁺(aq) have two single lines?Answer: Three phases meet: solid platinum, hydrogen gas and the solution. Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
Why is Pt written in Pt(s) | H₂(g) | H⁺(aq) || Cu²⁺(aq) | Cu(s)?Answer: Hydrogen gas and its ions give no solid to carry the electrons, so an inert platinum electrode does it. Source: LibreTexts Chemistry, general chemistry text map, 20.3 Voltaic Cells (cell diagrams, inert platinum electrode). Read 2026-10-03.
How this list was compiled: Questions, wrong choices and explanations were written for this site. The conventions (anode on the left, the reactant first in each half-cell, a single line for a phase boundary, a double line for the salt bridge, concentrations in parentheses, spectator ions left out, an inert electrode at the outer end) were read 2026-10-03 in: Purdue University, General Chemistry Topic Review, Electrochemical Cells (Line Notation for Voltaic Cells), https://chemed.chem.purdue.edu/genchem/topicreview/bp/ch20/electro.php; LibreTexts Chemistry, Cell Diagrams, and 20.3 Voltaic Cells of a general chemistry text map; and Wikipedia, Cell notation. Each cell asked is a spontaneous one: the anode was checked against the table of standard-state reduction potentials on the same Purdue page (or against a cell the LibreTexts page itself works, for cadmium, which that table does not list). No voltage is asked. Licence: own work
How it works
This cell diagram line notation practice asks what each part of a line such as Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s) means, and which line fits a given galvanic cell, with or without a platinum electrode.
Read the full guide
How a line is read
The anode half-cell is on the left and the cathode half-cell on the right, each with its electrode at the outer end. Inside a half-cell the reactant comes first. Left to right is the way the electrons go.
Two kinds of line
A single line is a boundary between two phases, such as a metal and a solution. The double line is the salt bridge between the half-cells.
Gases and platinum
A gas has no metal of its own to carry electrons, so an inert platinum wire is written at the outer end: Pt(s) | H₂(g) | H⁺(aq) for hydrogen at the anode.
Find what is oxidized in the reaction first: that species goes in the left half-cell.
Ions that take no part, such as nitrate, are not written.
Questions and answers
What is a cell diagram in chemistry?
A cell diagram, also called cell notation or line notation, is a one-line shorthand for a galvanic cell. It gives the electrodes and solutions by formula, from the anode on the left to the cathode on the right.
What do the single and double lines mean in cell notation?
A single vertical line is a phase boundary, for example between a solid electrode and its solution. A double vertical line is the salt bridge, or other junction, between the two half-cells.
Which side is the anode in cell notation?
The left. The anode half-cell, where oxidation happens, is written first and the cathode half-cell, where reduction happens, last, so the line reads the way the electrons flow.
How do you write cell notation for a hydrogen electrode?
As the anode, Pt(s) | H₂(g) | H⁺(aq); as the cathode, H⁺(aq) | H₂(g) | Pt(s). The platinum is an inert electrode at the outer end, and each single line is one phase boundary.
What is the cell notation for a zinc and copper cell?
Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s). Zinc is oxidized at the anode, on the left, and copper ions are reduced at the cathode, on the right. Concentrations go in parentheses: Zn²⁺(aq, 1.0 M).