Questions tagged [color]

Questions where color (wavelengths associated with the visible region of the electromagnetic spectrum of about 400-800nm), or a color change is discussed.

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Why is gold golden?

Bulk gold has a very characteristic warm yellow shine to it, whereas almost all other metals have a grey or silvery color. Where does this come from? I have heard that this property arises from ...
tschoppi's user avatar
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How can the intense color of potassium permanganate be explained with molecular orbital theory?

In the permanganate ion, manganese is in the $+7$ oxidation state, therefore it is a $\ce{d^0}$ ion. $\ce{d^0}$ and $\ce{d^1^0}$ ions don't absorb visible spectrum radiation because there are no ...
Nilay Ghosh's user avatar
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9 votes
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Colour intensity of transition metal complexes

Even though they are both $\mathrm{d^7}$ complexes, the colour of $\ce{[Co(H2O)6]^2+}$ is pale whereas that of $\ce{[CoCl4]^2-}$ is more intense. Does the octahedral or tetrahedral geometry matter in ...
Subhadip Pal's user avatar
24 votes
3 answers
35k views

Why are some salt solutions coloured?

I notice that salt solutions of $\ce{NaCl}$ and $\ce{KCl}$ are colourless while those of $\ce{CuSO4}$ and $\ce{FeSO4}$ are coloured. I got as far as figuring that it has to do with the transition ...
jokerdino's user avatar
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35 votes
3 answers
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Does O2 have a color in the gas phase

I have noticed that liquid $\ce{O2}$ (I clarify it as $\ce{O2}$ because oxygen exists in several other forms which have different colors in the liquid state than $\ce{O2}$) has a light blue color to ...
Caters's user avatar
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15 votes
2 answers
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Flame test: Is the metal atom or the metal ion responsible for the flame colour?

A sample of $\ce{CaCl2}$ is placed in the flame of a Bunsen burner. The component of the substance which is responsible for the production of the flame colour is: $\ce{Ca^2+}$ $\ce{Ca}$ $\ce{Cl-}$ $\...
confused's user avatar
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28 votes
2 answers
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Why is snow white?

I know that this is a rather ambiguous question; but my question is, whenever we take water and freeze it in the freezer, it still tends to stay clear. Since snow is just frozen water, why is it white?...
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16 votes
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Why is anhydrous copper(II) sulfate white while the pentahydrate is blue, even though both have one unpaired electron?

We all know that $\ce{CuSO4.5H2O}$ is blue and it turns to $\ce{CuSO4}$ on heating which is white. I also learnt about coordination complexes and d–d transitions and how transition metal compounds are ...
Kartik's user avatar
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How hydrate isomerism results difference in colours?

The standard example is $\ce{CrCl3.6H2O}$, which can have three distinctly different crystalline compounds now known as $\ce{[Cr(H2O)6]Cl3}$ (violet), $\ce{[CrCl(H2O)5]Cl .H2O}$ (blue-green), and ...
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18 votes
2 answers
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Color of chromate and permanganate

I've heard quite a few times that the chromate and permanganate have a $d^3s$ configuration. Also, their colors arise due to a rapid switching of electrons between the oxygen and metal atoms. I don't ...
ManishEarth's user avatar
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17 votes
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What is the reason for the blue color of an ammoniated electron?

I am quoting a line from a book regarding reactivity of alkali metals with liquid ammonia. The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible region ...
aman's user avatar
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5 answers
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Can flames be colored black?

Most of us here would know that flames can be colored by adding an appropriate salt to the 'fuel' or by simply introducing it into a flame. Boron and Barium salts give the flame a green tinge, ...
paracetamol's user avatar
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13 votes
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Why do s-block elements impart color to a flame?

Flame tests are a common way of identifying trace amounts of alkali metals (and to a lesser extent alkaline earth metals) in mixtures. Certain salts of $\ce{Ba, Sr}$ are also used in fireworks for ...
Gerard's user avatar
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9 votes
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Why lithium gives flame coloration?

Theoretically speaking, beryllium and magnesium does not give flame test because their atoms are comparatively smaller and the valance electrons are strongly attached to the nucleus. Therefore their ...
Nilay Ghosh's user avatar
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7 votes
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What is the chemical composition of Ferrous Ferrocyanide?

To this day, iron-cyanide complexes confuses me. So, I want to settle this once and for all. After scavenging the internet, I gathered the following result: $$ \ce{Ferr} \color{blue}{\ce{ous}}~\ce{...
Nilay Ghosh's user avatar
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3 votes
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Colored inorganic liquids: why is SCl2 red, and S2Cl2 orange?

Those do not involve d orbitals, so there is no crystal field theory or ligand theory. Do we have a name of study that only involves p orbitals? Since I think molecular theory is for all s p d f ...
Neal Conroy's user avatar
3 votes
2 answers
2k views

Iodine color change in different complexes

Why does the color of iodine differ when it forms a charge transfer complex with benzene (pi donor) - pink and ethanol (electron pair donor) - brown? Does the HOMO-LUMO energy differ, if so how?
EJC's user avatar
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1 vote
1 answer
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What does a molecules color have to do with its bond/orbital energies?

For example, elemental iodine is deep violet. Its sigma bond or perhaps the lone pairs are capable of absorbing all visible light frequencies except violet which is why we see it as that color. ...
Nova's user avatar
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30 votes
4 answers
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Why do transition elements make colored compounds?

Why do transition metals element make colored compounds both in solid form and in solution? Is it related to their electrons?
lambda23's user avatar
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25 votes
4 answers
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How may copper acetate ligands be manipulated to change colors?

I have a solution of copper acetate and I would like to play around with the ligands to get different colors. Background: The copper acetate was made through mixing vinegar (5% acetic acid), $\ce{...
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23 votes
4 answers
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Are there colorful metals besides gold and copper?

Are there yellow metals besides gold? Are there metals with color different than yellow and grey/silver or reddish?
Anixx's user avatar
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21 votes
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Why is manganese(II) coloured although the transition should be spin-forbidden?

In every basic coordination chemistry class, at some early point the crystal field theory and LFSE will be taught, explaining that there will be an energy difference between d-orbitals (typically ...
Jan's user avatar
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20 votes
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Why is nitrogen dioxide (NO2) brown? [closed]

I don't understand why nitrogen dioxide $\ce{NO2}$ is coloured brown when nitrate $\ce{NO2-}$ and dinitrogen tetroxide $\ce{N2O4}$ are not. I understand it is due to absorption of light when its ...
saatwik upadhyay's user avatar
17 votes
2 answers
4k views

What happens to electrons in metal complexes after excitation by visible light?

My book writes: When white light shines through a solution of a complex ion of a transition metal, photons of a particular frequency are absorbed and their energy promotes an electron from lower ...
Eliza's user avatar
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17 votes
1 answer
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What gives fresh milk a yellow tinge?

Every now and then, when I pop over to my grandparents' house, they make sure to give me a glass (or two) full of fresh milk (or "whole milk" if you will) and then proceed to pamper me for the rest of ...
paracetamol's user avatar
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13 votes
4 answers
15k views

What is the origin of the colour of azo dyes?

Is it the same reason as to why transition metal complexes have colour?
Eliza's user avatar
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12 votes
5 answers
26k views

Why does ZnO turn yellow when it is hot?

Why does ZnO's color become yellow when it is hot? I have read that it is because of physical properties, but I need a more elaborate explanation.
Kevin's user avatar
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12 votes
4 answers
6k views

Are complex ions thermochromic?

Does raising the temperature of a complex ion (formed from a transition metal ion and ligand(s)) affect its color? For example, if the temperature of $\ce{[Cr(H2O)6]^3+}$ is raised, will its color ...
sepehr78's user avatar
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12 votes
1 answer
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Colour of platinum

Why does platinum have silvery shine whereas platinum black (finely powdered platinum) is black in colour although both have the same constitution of pure platinum? Due to similar composition, both ...
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9 votes
1 answer
5k views

Why color of alkali metal peroxides, superoxides and ozonides deepens down the group?

This is basically a continuation of the question-"Why is potassium monoxide (K2O) coloured?" I knew that color of alkali metal oxides deepens down the group: Lithium oxide ($\ce{Li2O}$) is the ...
Nilay Ghosh's user avatar
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6 votes
1 answer
2k views

Can I synthesize iron acetate like this?

The oxidation state of the iron doesn't matter too much; I am just trying to make an attractive red-brown ink. Here are some instructions I prescribed to a friend. Here's an approximately decent ...
Simon Kuang's user avatar
4 votes
1 answer
14k views

Predicting color of precipitate

Is there any way of predicting whether a precipitate will be colored? I know that for solutions, transition metal ions with unfilled d-orbitals will have color because of d-orbital splitting in the ...
carbenoid's user avatar
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4 votes
1 answer
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Is chromium the shiniest metal?

I have seen many pictures of chromium, and it's pretty lustrous as I must say. Here are some examples. Is it the most lustrous metal known? Edit: By lustre, I mean suppose if we have a mirror ...
Pritt says Reinstate Monica's user avatar
4 votes
1 answer
2k views

Color imparted to flame and color of coordination compounds

When we heat a ionic substance/compound, the ionic bond gets weakened and the metal is ionized. Is the color imparted to the flame due to absorption of light? i.e. Do we see the remaining wavelengths? ...
Quark's user avatar
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3 votes
2 answers
17k views

Does a calibration curve of absorbance vs concentration need to pass exactly through the origin?

If you are making a calibration curve for $\ce{CuSO4}$ where you plot absorbance against concentration and the curve deviates slightly from the origin, does it make the calibration curve useless?
Prosti 's user avatar
2 votes
2 answers
865 views

The color of the most sulfides of p- and d-block elements

My teacher said that many of the sulfides of d-block and p-block are black. Why?
Adithya's user avatar
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1 vote
1 answer
5k views

How can we predict the colour of transition metal complexes?

I am facing problems in indentifying colour of complex compunds just by seeing the their molecular formula. Is there any method or concept to predict the colour of complex compunds?
Aviral Agarwal's user avatar
1 vote
1 answer
4k views

What is the colour of chromium(III) chloride solution?

I had a question asking about the colour of the solution of chromium(III) chloride in my exam, all my colleagues have different answers, I couldn't find any exact answer after searching!
mohammed mokhtar's user avatar
86 votes
5 answers
20k views

Is it true that heavy water is not blue?

I believe I saw this claim somewhere on the internet a long time ago. Specifically, it was claimed that the difference could be observed by filling one long, straight tube with light water and one ...
Brian's user avatar
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23 votes
1 answer
22k views

What makes ABS plastic turn yellow?

If you owned old kitchen appliances or old computer you might notice that they the once cream white plastic become increasingly yellow, old and disgusting. I have read that UV lighting can damage ...
nabulator's user avatar
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21 votes
1 answer
9k views

What causes the iridescent colour in laboratory grown bismuth?

Artificially grown bismuth crystals are arguably magnificent, as seen in the image below: Image source: Minerals.net The website states that: They have hopper-like growths in pseudocubic crystals ...
user avatar
18 votes
3 answers
20k views

Why are acids usually depicted in fiction as green?

In cartoons, etc., acid is generally shown as vividly green, as in this scene from the Simpsons: We even have the colour "acid green". But when I used to use acids in chemistry class, they weren't ...
Au101's user avatar
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15 votes
1 answer
25k views

Why does copper precipitate out as a pink solid?

When copper is precipitated out of a solution e.g from CuI, why does it appear pink instead of copper-coloured? Are there other situations where copper appears pink in solid form?
Naim Sen's user avatar
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15 votes
1 answer
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Why/how is blood red? (colours of hemoglobin)

Oxyhaemoglobin is red, deoxyhaemoglobin is bluish-purple, and carboxyhaemoglobin is a cherry red colour. Evidently in the porphyrin around the iron molecule in heme there is a conjugated $\pi$-system ...
James Harrison's user avatar
14 votes
1 answer
1k views

Why do some materials turn black and others white after combustion?

Most solids objects turn black after they are burnt. But some turn white. Why is that ?
mick's user avatar
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14 votes
1 answer
7k views

Does bleach turn a substance white or colorless?

From what I understand, bleach works to weaken the ability of a substance to absorb light. Thus this seems to be "whitening" i.e. reflecting all light. In contrast, colorlessness (according to ...
Jet Blue's user avatar
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14 votes
1 answer
21k views

Color changes of a solution of acetone and sodium hydroxide

I have put acetone and sodium hydroxide solution (approximately $\pu{1M}~ \ce{NaOH}$) in a beaker and didn't see any colour change for a day (actually, it was transparent, no colour). After almost 2 ...
user avatar
12 votes
1 answer
522 views

Allotropes of Phosphorus

Something I noticed whilst revising about group 15 is that the darker the allotrope of phosphorus, the more stable it is. white/yellow – very volatile, soluble, pyrophoric red – air ...
Codefailure's user avatar
10 votes
0 answers
879 views

What is the chemistry behind black colour of platinum black? [duplicate]

Platinum is a silvery white metal and is highly unreactive then why it's powdered form "platinum black" is platinum metal but is black in colour. why would a metal such as platinum become black as a ...
JM97's user avatar
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9 votes
2 answers
4k views

Why is the photon energy of lithium flame coloring lower than that of cesium?

Why does $\ce{Li}$ give a red flame color which has lower photon energy compared to $\ce{Cs}$ which gives a violet flame color according to $E=h\nu$? This is my attempt: Since lithium has smaller ...
Brett Leigh's user avatar