Nitric Acid Acts Upon Copper

Nitric Acid Acts Upon Copper

While reading a textbook of chemistry I While reading a textbook of chemistry I came upon the statement, "nitric acid acts came upon the statement, "nitric acid acts upon copper." I was getting tired of upon copper." I was getting tired of reading such absurd stuff and I was reading such absurd stuff and I was determined to see what this meant. determined to see what this meant. Copper was more or less familiar to me, Copper was more or less familiar to me, for copper cents were then in use. I had for copper cents were then in use. I had seen a bottle marked nitric acid on a table seen a bottle marked nitric acid on a table in the doctor's office where I was then in the doctor's office where I was then "doing time.""doing time."

I did not know its peculiarities, but the I did not know its peculiarities, but the spirit of adventure was upon me. Having spirit of adventure was upon me. Having nitric acid and copper, I had only to learn nitric acid and copper, I had only to learn what the words "act upon" meant. The what the words "act upon" meant. The statement "nitric acid acts upon copper" statement "nitric acid acts upon copper" would be more than mere words.would be more than mere words.

All was still. In the interest of knowledge All was still. In the interest of knowledge I was even willing to sacrifice one of the I was even willing to sacrifice one of the few copper cents then in my possession. I few copper cents then in my possession. I put one of them on the table, opened the put one of them on the table, opened the bottle marked nitric acid, poured some of bottle marked nitric acid, poured some of the liquid on the copper and prepared to the liquid on the copper and prepared to make an observation. But what was this make an observation. But what was this wonderful thing which I beheld?wonderful thing which I beheld?

The cent was already The cent was already changed and it was no changed and it was no small change either. A small change either. A green-blue liquid foamed green-blue liquid foamed and fumed over the cent and fumed over the cent and over the table. and over the table. The air in the neighborhood of the The air in the neighborhood of the performance became colored dark red. A performance became colored dark red. A great colored cloud arose. This was great colored cloud arose. This was disagreeable and suffocating. How should disagreeable and suffocating. How should I stop this?I stop this?

I tried to get rid of the objectionable mess I tried to get rid of the objectionable mess by picking it up and throwing it out of the by picking it up and throwing it out of the window. I learned another fact. Nitric window. I learned another fact. Nitric acid not only acts upon copper, but it acts acid not only acts upon copper, but it acts upon fingers. The pain led to another upon fingers. The pain led to another unpremeditated experiment. I drew my unpremeditated experiment. I drew my fingers across my trousers and another fingers across my trousers and another fact was discovered. Nitric acid acts upon fact was discovered. Nitric acid acts upon trousers. trousers.

Taking everything into consideration, Taking everything into consideration, that was the most impressive experiment that was the most impressive experiment and relatively probably the most costly and relatively probably the most costly experiment I have ever performed... It experiment I have ever performed... It was a revelation to me. It resulted in a was a revelation to me. It resulted in a desire on my part to learn more about desire on my part to learn more about that remarkable kind of action. Plainly, that remarkable kind of action. Plainly, the only way to learn about it was to see the only way to learn about it was to see its results, to experiment, to work in a its results, to experiment, to work in a laboratory.laboratory. Ira RemsenIra Remsen

Ira Remsen, born in New York City in Ira Remsen, born in New York City in 1846, was originally trained as a 1846, was originally trained as a medical doctor but left that field to study medical doctor but left that field to study chemistry and went on to become a chemistry and went on to become a leader in chemical education and leader in chemical education and research and to become the president of research and to become the president of Johns Hopkins University. He was the Johns Hopkins University. He was the accidental discoverer of saccharin, an accidental discoverer of saccharin, an artificial sweetener.artificial sweetener.

The nitric The nitric acid itself acid itself

is dangerous.is dangerous.

The brown gas is toxic.

Use a fume hood!

The brown gas is toxic.

Now you are going to see how Now you are going to see how nitric acid acts upon copper.nitric acid acts upon copper.

Several copper pennies will be Several copper pennies will be placed into a solution of placed into a solution of concentrated nitric acid.concentrated nitric acid.

What is the formula for nitric acid?What is the formula for nitric acid?

HNOHNO33

The 18M stock The 18M stock solution of solution of nitric acid.nitric acid.

A 4M solution of A 4M solution of nitric acid.nitric acid.

Copper pennies.Copper pennies.

The pennies are The pennies are placed into a placed into a beaker of nitric beaker of nitric acid, HNOacid, HNO33, in a , in a

fume hood.fume hood.

A watch glass A watch glass makes the gas makes the gas more visible.more visible.

Check out the Check out the temperature temperature change.change.

What changes What changes do you observe do you observe in the liquid?in the liquid?

This sample This sample went from went from

22C to 38C.22C to 38C.

The reaction is The reaction is stopped by stopped by removing the removing the pennies..pennies..

What changes What changes do you observe do you observe in the pennies?in the pennies?

How has the How has the liquid phase liquid phase changed?changed?

With what With what acids will acids will copper react?copper react?

What accounts What accounts for the color?for the color?

The pennies The pennies used must used must have been have been minted before minted before 1982.1982.

Why?Why?

Cu(s) + HNOCu(s) + HNO33(aq)(aq)

State symbolsState symbols

(s) = solid(s) = solid

(l) = liquid(l) = liquid

(g) = gas(g) = gas

(aq) = aqueous solution(aq) = aqueous solution

HNOHNO33 has a definite composition. has a definite composition.

Copper, Cu, is an element.Copper, Cu, is an element.

HNOHNO3 3 is a compound called is a compound called

nitric acid. nitric acid.

When it is dissolved in water, it When it is dissolved in water, it forms an aqueous solution.forms an aqueous solution.


When nitric acid, HNOWhen nitric acid, HNO33, is dissolved in water, it , is dissolved in water, it

separates completely into ions.separates completely into ions.

What are ions?What are ions?

Ions are charged atoms or Ions are charged atoms or groups of atoms. They have groups of atoms. They have a charge because they have a charge because they have gained or lost electrons.gained or lost electrons.

In aqueous solution HNOIn aqueous solution HNO33 exits as separate exits as separate

hydrogen ions, Hhydrogen ions, H++, and nitrate ions, NO, and nitrate ions, NO33--..

When nitric acid, HNOWhen nitric acid, HNO33, reacts with copper , reacts with copper

metal, copper ions, Cumetal, copper ions, Cu2+2+ are formed. are formed.

In addition, nitrogen monoxide gas, In addition, nitrogen monoxide gas, NO, is formed, along with liquid water.NO, is formed, along with liquid water.

The equation begins to look like this:The equation begins to look like this:



Cu(NOCu(NO33))22(aq) + NO(g) + H(aq) + NO(g) + H22O(l)O(l)Products

Reactants

Cu(NOCu(NO33))22(aq) + NO(g) + H(aq) + NO(g) + H22O(l)O(l)


Cu(NOCu(NO33))22 is called is called

copper(II) nitrate. The copper(II) nitrate. The soluble salt exists as soluble salt exists as copper ions, Cucopper ions, Cu2+2+ and and nitrate ions, NOnitrate ions, NO33

--, in , in

aqueous solution.aqueous solution.

How do we detect the presence of ions?How do we detect the presence of ions?

The light bulb The light bulb conductivity conductivity

tester lights up tester lights up when ions when ions

conduct conduct electricity.electricity.



Demo: Demo:

1.1. Test conductivity of pure water.Test conductivity of pure water.

2.2. Add nitric acid to pure water.Add nitric acid to pure water.

3.3. Dissolve solid Cu(NODissolve solid Cu(NO33))22 in pure in pure

water.water.



There is something wrong There is something wrong with this chemical equation.with this chemical equation.

It isn’t balanced.It isn’t balanced.

The law of conservation of matter (or mass) The law of conservation of matter (or mass) says that every atom must be accounted for.says that every atom must be accounted for.

Adjust the coefficients to even up the atoms.Adjust the coefficients to even up the atoms.

Hint: A 3 goes there.Hint: A 3 goes there.

33



There is something wrong There is something wrong with this chemical equation.with this chemical equation.

It isn’t balanced.It isn’t balanced.

The law of conservation of matter (or mass) The law of conservation of matter (or mass) says that every atom must be accounted for.says that every atom must be accounted for.

Adjust the coefficients to even up the atoms.Adjust the coefficients to even up the atoms.

Hint: A 3 goes there.Hint: A 3 goes there.

33

Come, come. Balance the

equation before going on.

3388882424

33Cu(NOCu(NO33))22(aq) + (aq) + 22NO(g) + NO(g) + 44HH22O(l)O(l)

Cu(s) + Cu(s) + 88HNOHNO33(aq)(aq)

When the equation is balanced, these will be the When the equation is balanced, these will be the coefficients.coefficients.

33

3388882424

CuCuHHNNOO

ReactantsReactants ProductsProducts

Count Count the the

atomsatoms

3Cu(NO3Cu(NO33))22(aq) + 2NO(g) + 4H(aq) + 2NO(g) + 4H22O(l)O(l)

What are some What are some indications that indications that a chemical a chemical reaction has reaction has taken place?taken place?

3Cu(s) + 8HNO3Cu(s) + 8HNO33(aq)(aq)

1.1. A gas is given offA gas is given off2.2. A color change occursA color change occurs3.3. A temperature change occursA temperature change occurs

A fourth indicator of a chemical A fourth indicator of a chemical reaction didn’t occur here. It is reaction didn’t occur here. It is the formation of an insoluble the formation of an insoluble precipitate.precipitate.


We saw the We saw the temperature of temperature of the solution the solution increase. Was increase. Was energy energy absorbed or absorbed or released by this released by this reaction?reaction?


Energy was given off in the Energy was given off in the reaction, which accounted for reaction, which accounted for the rise in temperature.the rise in temperature.

Reactions that give off energy Reactions that give off energy are are exothermicexothermic..Reactions that absorb energy Reactions that absorb energy are are endothermicendothermic..


This is called a “molecular equation” because This is called a “molecular equation” because everything is written as molecules, but it doesn’t everything is written as molecules, but it doesn’t take into account that some substances exist as take into account that some substances exist as ions in aqueous solution.ions in aqueous solution.


A better way to write is as A better way to write is as an ionic equation.an ionic equation.



3Cu3Cu2+2+ + 6NO + 6NO33-- + 2NO(g) + 4H+ 2NO(g) + 4H22O(l)O(l)

3Cu(s) + 8H3Cu(s) + 8H++ + 8NO + 8NO33--

Now, everything that Now, everything that exists as an ion, is written exists as an ion, is written

as an ion.as an ion.


3Cu(s) + 8H3Cu(s) + 8H++ + 8NO + 8NO33--

But NO gas is a colorless gas. Where does But NO gas is a colorless gas. Where does the brown gas come from?the brown gas come from?

The reaction is between the atoms of copper The reaction is between the atoms of copper and the nitrate ion. This produces copper ions and the nitrate ion. This produces copper ions and NO gas.and NO gas.

And NOAnd NO22 is a reddish-brown, vile smelling, is a reddish-brown, vile smelling,

somewhat toxic gas.somewhat toxic gas.

There is a “side-reaction”, in which NO gas There is a “side-reaction”, in which NO gas reacts with the oxygen gas, Oreacts with the oxygen gas, O22, in the air to , in the air to

make NOmake NO22..

2NO(g) + O2NO(g) + O22(g)(g) 2NO2NO22(g)(g)


3Cu(s) + 8H3Cu(s) + 8H++ + 8NO + 8NO33--

This is the first reaction in a series of This is the first reaction in a series of reactions that you will be doing in a lab called reactions that you will be doing in a lab called the “Copper Cycle”.the “Copper Cycle”.

No, not that kind of cycle.No, not that kind of cycle.

The The Copper Copper CycleCycle

A series of reactions A series of reactions involving copper involving copper

where the reactants in where the reactants in one step are the one step are the

products from the products from the previous step.previous step.

Copper Lab

Balancing EquationsEvidence of

reaction

Types of reactions

Predicting products

Acid/base neutralization

Net ionic equations

REDOX

Reaction rate factors

pH and [H+]

Stoichiometry

Activity series

Solubility rules

Acids

Stock system

Nomenclature

1. Precipitate2. Gas given off3. Temperature change4. Color change

1. Synthesis2. Decomposition3. Single replacement4. Double replacement5. Combustion of a hydrocarbon

1. Concentration2. Temperature3. Surface area4. Catalyst

Thermodynamics Endothermic & exothermic

Reaction pathway diagramsActivation energy

Oxidizing and reducing agents

Strong & weak

The Copper Cycle LabThe Copper Cycle Lab

Comments or questions may be directed to

Mike JonesPisgah High School

Canton NC

[email protected]

07/13/0506/02/10

Rev. 011812

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Nitric Acid Acts Upon Copper

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