Title: Module 2: Battery Chemistry & Electrolyte - Quiz
Course: ASE A6 Battery Service > Section: Module 2: Battery Chemistry & Electrolyte

Q: During discharge, both the positive and negative plates convert to:
- Lead dioxide (PbO2)
- Sponge lead (Pb)
- Lead sulfate (PbSO4)
- Sulfuric acid (H2SO4)
A: Lead sulfate (PbSO4)
Feedback: During discharge, both plates convert to lead sulfate (PbSO4). The sulfate ions come from the electrolyte.

Q: During battery discharge, the electrolyte:
- Gets stronger as acid is produced
- Gets weaker as acid is consumed and water is produced
- Stays the same concentration
- Evaporates and must be replaced
A: Gets weaker as acid is consumed and water is produced
Feedback: Sulfuric acid is consumed during discharge and water is produced, making the electrolyte weaker (lower specific gravity).

Q: The specific gravity of a fully charged lead-acid battery is approximately:
- 1.000
- 1.120
- 1.190
- 1.265
A: 1.265
Feedback: Fully charged electrolyte has an SG of approximately 1.265. An SG of 1.120 indicates a discharged battery, and 1.000 is pure water.

Q: Technician A says during charging, lead sulfate on the plates converts back to the original active materials. Technician B says during charging, water is consumed and sulfuric acid is regenerated in the electrolyte. Who is correct?
- Technician A only
- Technician B only
- Both Technician A and Technician B
- Neither Technician A nor Technician B
A: Both Technician A and Technician B
Feedback: Both are correct. Charging reverses the discharge reaction: lead sulfate converts back to lead dioxide (positive) and sponge lead (negative), while sulfate ions return to the electrolyte, regenerating the acid.

Q: A battery has been sitting overnight. The open-circuit voltage reads 12.2V. This indicates a state of charge of approximately:
- 100%
- 75%
- 50%
- 25%
A: 50%
Feedback: An OCV of 12.2V corresponds to approximately 50% state of charge. 12.6V = 100%, 12.4V = 75%, 12.0V = 25%.

Q: During discharge at the positive plate, lead dioxide (PbO₂) reacts with sulfuric acid to form:
- Sponge lead (Pb) and water
- Lead sulfate (PbSO₄) and water
- Lead oxide (PbO) and hydrogen gas
- Pure lead (Pb) and sulfuric acid
A: Lead sulfate (PbSO₄) and water
Feedback: At the positive plate during discharge, lead dioxide reacts with sulfate ions from the acid to form lead sulfate and water. This is why the electrolyte weakens during discharge — acid is consumed and water is produced.

Q: Since most modern automotive batteries are sealed, the primary method used to determine state of charge is:
- Measuring electrolyte level
- Measuring open-circuit voltage with a voltmeter
- Measuring current draw with an ammeter
- Checking the electrolyte color
A: Measuring open-circuit voltage with a voltmeter
Feedback: Sealed (maintenance-free) batteries have no access to the electrolyte for direct testing. Open-circuit voltage, measured after the battery has rested, is the primary method to determine state of charge.

Q: During the charge reaction, which of the following happens inside the battery?
- Lead sulfate on both plates converts back to the original active materials
- Water in the electrolyte is converted to sulfuric acid
- Sulfate ions move from the plates back into the electrolyte
- All of the above
A: All of the above
Feedback: Charging reverses the discharge reaction. Lead sulfate converts back to lead dioxide (positive plate) and sponge lead (negative plate), sulfate ions return to the electrolyte, and water is consumed to regenerate the sulfuric acid.

Q: At the negative plate during discharge, sponge lead (Pb) reacts with sulfuric acid to form:
- Lead dioxide (PbO₂) and oxygen
- Lead sulfate (PbSO₄) and hydrogen ions
- Pure lead (Pb) and water
- Lead oxide (PbO) and sulfuric acid
A: Lead sulfate (PbSO₄) and hydrogen ions
Feedback: At the negative plate during discharge, sponge lead reacts with sulfate ions from the acid to form lead sulfate. The hydrogen ions released combine with oxygen at the positive plate to form water.

Q: Technician A says the electrolyte gets weaker during discharge because sulfate ions leave the acid and attach to the plates. Technician B says the electrolyte gets stronger during charging because sulfate ions return from the plates to the acid. Who is correct?
- Technician A only
- Technician B only
- Both Technician A and Technician B
- Neither Technician A nor Technician B
A: Both Technician A and Technician B
Feedback: Both are correct. During discharge, sulfate ions leave the electrolyte and combine with the plate materials to form lead sulfate, weakening the acid. During charging, the reverse occurs — sulfate ions return to the electrolyte, strengthening it.

Q: During the discharge reaction, electrons flow:
- From the positive plate through the external circuit to the negative plate
- From the negative plate through the external circuit to the positive plate
- From the electrolyte through both plates
- From the separator to the electrolyte
A: From the negative plate through the external circuit to the positive plate
Feedback: During discharge, the negative plate releases electrons that flow through the external circuit (powering the load) to the positive plate. Inside the battery, ions carry current through the electrolyte.

Q: The electrolyte in a lead-acid battery:
- Only conducts electricity and does not participate in the chemical reaction
- Is an active participant that supplies and receives sulfate ions
- Must be replaced every 12 months
- Is the same concentration regardless of charge state
A: Is an active participant that supplies and receives sulfate ions
Feedback: The electrolyte is an active participant. It supplies sulfate ions to the plates during discharge and receives them back during charging. Its concentration directly reflects state of charge.

Q: A specific gravity reading of 1.120 indicates:
- A fully charged battery
- A battery at 75% charge
- A battery at 50% charge
- A discharged battery
A: A discharged battery
Feedback: An SG of 1.120 indicates a fully discharged battery. The electrolyte has lost most of its acid to the plates as lead sulfate.

Q: A lead-acid battery is rechargeable because:
- The electrolyte can be drained and replaced with fresh acid
- The chemical reactions at both plates are reversible
- The plates are made of materials that never wear out
- An external voltage replaces the electrolyte that was lost
A: The chemical reactions at both plates are reversible
Feedback: A lead-acid battery is rechargeable because the discharge reactions are reversible. Applying an external voltage during charging converts lead sulfate back to the original active materials (lead dioxide and sponge lead) and regenerates the sulfuric acid.

Q: What is the open-circuit voltage of a battery with a specific gravity of 1.225?
- 12.0V
- 12.2V
- 12.4V
- 12.6V
A: 12.4V
Feedback: An SG of 1.225 corresponds to approximately 75% state of charge, which corresponds to an open-circuit voltage of 12.4V.