The weight loss of an aluminum alloy corroding in a solution of hydrochloric acid was observed to be 0.250 g/cm2 after an 8 h immersion period [13]. What is the corresponding anodic current density in milliamperes per square centimeter, assuming that all the corrosion is due to the following anodic half-cell reaction:

This question is incomplete, the complete question is;

The weight loss of an aluminum alloy corroding in a solution of hydrochloric acid was observed to be 0.250 g/cm² after an 8 h immersion period [13]. What is the corresponding anodic current density in milliamperes per square centimeter, assuming that all the corrosion is due to the following anodic half-cell reaction:

Al → Al³⁺ + 3e⁻

The atomic weight is 58.7 g/mol

Current density in milliamperes per square centimeter is 45.81 mA/cm²

Explanation:

Given the data in the question;

we know that Faradays law of electrolysis states that;

amount of substance produced at each electrode is directly proportional to the quantity of charge flowing through the cell.

so

m = ( Q/F) (M/z)

where m is the mass of substance liberated at an electrode( 0.250 g/cm²)

Q is the total electric charge passed through the substance

F is Faradays constant (96,500 C/mol)

M is the molar mass of the substance( 58.7 g/mol )  and Z is the number of electrons transferred(3)

Also

we know that; Q = It

where I is current and t is time( 8hrs × 60 × 60 = 28800 sec )

we substitute  Q = It  into our equation'

we have;

m = ( It/F) (M/z)

m = ItM / Fz

mFz = ItM

I = mFz / tM

so we substitute

I = [0.250 g/cm² × 96,500 C/mol × 3] / [ 28800 × 58.7 g/mol]

I = 72375 /  1690560

I = 0.04581 A/cm²

we know that; 1 ampere = 1000 milliampere

so

I = 0.04581 × 1000

I = 45.81 mA/cm²

Therefore, current density in milliamperes per square centimeter is 45.81 mA/cm²

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.