Why does lead only react with a very dilute nitric acid but not concentrated nitric acid?

It forms Copper II Nitrate Cu(NO3)2 if reacted with nitric acid in any concentration - it’s not the usual metal - acid reaction though, as it produces oxides of Nitrogen and water rather than hydrogen, due to the NO3- anions oxidising the metal.

In dilute concentrations, nitrogen monoxide is produced:

3Cu + 8HNO3 ⟶ 3Cu(NO3)2 + 2NO + 4 H2O

and in concentrated form, nitrogen dioxide is given off:

Cu + 4HNO3 ⟶ Cu(NO3)2 + 2NO2 + 2H2O

No. The process for making esters involves extracting a water molecule from the two reactants. If there is too much water present, then it will be consumed instead. This would be true of any diluted acid.

an oxidizing agent is a chemical substance that removes one or more electrons from another atom

Conc Nitric acid reacts with copper

4 HNO3 + Cu ==> Cu(NO3)2 + 2 NO2 + 2 H2O

Oxidation state(OS)of nitrogen is +5 in reactants

And in products it is

Nitrate -1

NO2 +4

Dil Nitric acid reacts with copper

3Cu + 8HNO3 ==> 3Cu(NO3)2+ 2NO + 4H2O

OS of nitrogen is +5 in reactants

And in products it is

Nitrate -1

NO +2

The oxidation states which are mentioned are for nitrogen only.

Since conc nitric acid gives a product of nitrogen which has more oxidation number than the product of diluted nitric acid

Conc HNo3 is a strong oxidizing agent than dil HNo3

Similar results are observed when

H2S gas is bubbled through dilute and concentrated HNO3.

Dilute HNo3 gives NO and a colorless solution becomes turbid due to formation of colloidal solution with sulphur

Conc HNO3 gives NO2

Cheers!!

Correct me if i’m wrong….

Lead will react with concentrated nitric acid. Trust me.

Nitric acid reacts with copper according to the reaction: 4 HNO3(l) + Cu(s) ==> Cu(NO3)2(s and aq) + 2 NO2(g) + 2 H2O(l) The copper nitrate salt that forms is a deep blue color. The nitrogen dioxide is a orange vapor.

Nitric acid is an acid, but it also is a powerful oxidizing agent. Nitrogen in HNO3 is in +5 oxidation state, and is looking to add electrons (get reduced). Lead metal is a somewhat active reductant (it is a metal after all), since it can donate electrons (get oxidized) and get up to +2 [Pb (II)] or +4 [Pb (IV)] oxidation state.

When Pb metal reacts with dilute HNO3, a redox reaction takes place, and Pb(NO3)2 + NO + H2O is formed. Nitric oxide (NO) can react further with oxygen in the air to form nitrogen dioxide (NO2).

When concentrated HNO3 is used with lead metal, formation of PbO (lead oxide) is favored. Lead oxide is insoluble in acid, and forms a coating over the residual metal, rendering it inactive (inaccessible to acid). Therefore, no apparent reaction is observed.

PbO formed above can react further with HNO3 to produce Pb(NO3)2, NO2 + H2O. However, this might require the use of finely divided Pb metal to start the reaction.

You cannot concentrate nitric acid by distillation to 100%, because of a eutectic point is reached when it gets up to 98% concentration (azeotrope is a mixture of two liquids that boils at constant temperature). So, there is no way to separate HNO3 from H2O beyond the 98% mixture by distillation.

There are ways to dehydrate a mixture without boiling it. One way is to add a desiccant (something that absorbs water from a mixture), as long as the desiccant is not going to react with the substrate, and can sequester the water without releasing it back into the mixture.

For example, if you use anhydrous copper sulfate, you can remove water from a mixture containing a few ppm of water. For nitric acid, a desiccant material such as conc. H2SO4 can achieve some level of dehydration, and result in ~ 99.5% pure nitric acid. This material is called “fuming nitric acid”, and it still contains some level of water in it. Fuming nitric acid can dissociate into nitrogen oxides if it is exposed to light, even at 99.5%

Any further removal of the remaining ~ 0.5% of water from 99.5% fuming HNO3 will result in decomposition of HNO3 to form its component nitrogen oxides by release of water - NO2 and NO. This is the reason why you cannot achieve 100% HNO3.

It is what it is. A liquid with a concentration of 60% nitric acid. It isn’t “fuming nitric acid” (about 100%) and it isn’t the more common 68% industrial use acid.

What it is, is very dangerous indeed. Highly corrosive.Dissolves metal, clothing, and you. Generating poisonous gas while it does so.

False assumption.

Understand that dilute nitric acid is a solution of HNO3 in water. Concentrated nitric acid is a solution of H2O in HNO3. Standard lab “conc HNO3” is about 68% HNO3 and 32% H2O.

The solubility of lead nitrate in 5% HNO3 is about 25% -very soluble. The solubility in 68% is about 0.03% - largely insoluble. (It is even less soluble in higher concentrations.)

Thus if lead dissolves to make lead nitrate the liquid becomes saturated very quickly in concentrated acid and the reaction stops. In dilute acid, there is plenty of room. (However, the reaction is slow.)

The other possible reaction comes from the oxidizing nature of HNO3, which gives lead oxide, which is insoluble.

Potassium nitrate (KNO3) is a neutral salt formed by nitric acid (HNO3), which is a strong acid, and a strong potassium base such as KOH. Hence, KNO3 cannot undergo hydrolysis and will not react with HNO3 as an acid-base neutralization reaction.

Also, KNO3 and HNO3 have the same ion, NO3-, and therefore, will not exchange ions when mixed together.

So nope. They don’t react.