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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Material to change its color by temperature condition meets over time

There are thermochromic materials which their color changes reversible by temperature. Simply they show their current temperature by color. We can say their color is a function of current temperature: ...
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1answer
105 views

Clarification on absorption spectra and crystal field theory

My textbook, Chemistry: The Central Science, gives this figure to explain the purple color of the hexaaquatitanium(III) ion: Such absorption spectra are common to chemistry and biochemistry. ...
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24 views

Transition Metals colours and electron absorbtion

I understand that when d-orbitals split some electrons can occupy the higher orbitals by absorbing frequencies of light, but do these electrons then fall back to their original ground states? If so, ...
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1answer
48 views

Are there biodegradable pigments that are soluble in oil, but not in water?

I'm hoping to find a purple pigment that preferably, but not necessarily, can be used at room temperature. The goal is a pigment that will break down in septic systems.
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2answers
26 views

Which single organic molecule has strong absorbance throughout the visible range?

Is there a single organic molecule that has strong absorbance throughout the visible range? For example a black dye that is based on a single molecule?
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1answer
114 views

Failed esterification of 1-butanol and ethanoic acid

I did an esterification experiment of 1-butanol and ethanoic acid. 30 mL of 1-butanol was added followed by 30 mL of ethanoic acid, and then 1.5 mL of concentrated sulphuric acid and some boiling ...
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0answers
29 views

How does the “methylamine test for sugars” work exactly?

There is a test that enables distinction of sugars between mono- and oligosachharides. It consists letting methylamine react with an aqueous solution of the sugar under alkalic conditions and ...
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1answer
87 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!
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1answer
65 views

Which alcohols change CrO3/H2SO4 from orange to green? [closed]

Which of the following sets of compounds cannot turn a clear orange solution of $\ce{CrO3/H2SO4}$ to a greenish opaque solution? (More than one answer is correct) A) Ethanol B) 2-...
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1answer
65 views

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. ...
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1answer
61 views

How potassium ferrocyanide is coloured?

The colour of a complex compound is due to unpaired electrons. As per crystal field theory, $\ce{K4[Fe(CN)6]}$ has no unpaired electrons so it has to be colourless. But then why is it coloured?
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427 views

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 ...
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1answer
73 views

Why is MnSO4 colourless?

I get it that transition metal salts have colour due to d-d transition from $\mathrm{t_{2g}}$ to $\mathrm{e_g}$ orbitals in octahedral and the opposite in tetrahedral but why would $\ce{Mn^2+}$ not ...
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1answer
43 views

Why do colored solutions become more transparent as volume is decreased?

For instance, I was drinking Gatorade, and as I drank more and more, the drink became lighter in color. Why? I don't understand. I would think that the molarity stays constant and the color too. I ...
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0answers
42 views

What gives variations in the color of cadmium sulfide paint pigment?

Oil paint manufacturers sometimes make several "shades" of a color, all of which list the exact same chemical ingredient. For example, look at Gamblin's artist grade oils, in the yellow colors, ...
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1answer
63 views

What chemical properties that allow for colour exist in the dark?

Of course if there's no light around, there's no colour that you can see. On the other hand, the wall must have some property that makes it be blue. That property is still there in the dark. — ...
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0answers
27 views

Special effects: using non-toxic solutions to create colors

I'm looking for a non-toxic solution to create low budget special effects without using digital effects. An actor ($175\: \mathrm{cm}$ tall) could: wear a particular kind of clothing? be coated ...
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1answer
940 views

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 ...
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15 views

Why do Aerozine and dinitrogen tetroxide burn with a colorless flame?

Here is a launch of the Titan II ICBM: (Image Source: Wikipedia) Wikipedia says: The Titan II also used storable propellants: Aerozine 50, which is a 1:1 mixture of hydrazine and unsymmetrical ...
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1answer
94 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 ...
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39 views

How can methyl salicylate be found in 3 different colours? [closed]

Methyl salicylate can be colourless, yellow or red. What determines the colour changes?
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40 views

How do we see coordination complex colors?

The color of a coordination complex can be predicted using the Crystal Field Theory. The basic principle involved in this is that complexes absorb certain wavelengths of light and transmit the other ...
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32 views

What does a molecules color have to do with its bond/orbital energies?

For example, elemental iodine is deep violet. It's 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. ...
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57 views

Why is tin(IV) iodide bright orange while elemental iodine is violet?

Does it have anything to with iodines polarizability? Is there a way to explain this using sigma bonding or an MO diagram?
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2answers
176 views

Colour due to F-centre is same as that produced in a flame test, why?

I have noticed that the colours that the F-centres impart in Alkali metal halides are the same that the corresponding alkali metals impart to their flames. $\ce{NaCl}$ when heated in an atmosphere of ...
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2answers
54 views

Photosynthesis: Chlorophyll and color. [closed]

As I know, chlorophyll is green as it absorbs all wavelengths but green. It absorbs red, yellow, blue, purple, etc. Thus, the plant does not utilize green light. i] Why is chlorophyll green? Is ...
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1answer
99 views

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

Platinum is a silvery white metal and is highly unreactive then why it's powdered form "platinum black" is black in colour?
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606 views

CuCl2 has colour but CuCl does not

$\ce{CuCl2}$ is green in colour while $\ce{CuCl}$ is white. What is the reason for this? Is it because the first compound exists as a complex ion and has d-d transitions?
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1answer
59 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? ...
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176 views

Are there any colorful, odorless gases?

Gases are frequently described as "colorless, odorless, and tasteless." I am wondering if this is redundant, since I can't think of many gases that have a detectable color to begin with, much less ...
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1answer
125 views

How does complex ion differ from ligand complex?

As I understand, in terms of "colouring", ligand complex cause a transition metal cation centre's d-shell to split, allowing the electrons in that region to absorb specific frequencies of light, and ...
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1answer
165 views

Color of Anhydrous Transition Metal Salt

Why are some anhydrous transition metal salts colored? Here are some examples I found. Anhydrous cobalt(II) chloride ($\ce{CoCl2}$), with sky-blue color. Anhydrous chromium(III) chloride ($\ce{...
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76 views

Increasing Covalent character increases Colour intensity

I observed some trends as follows:- $\ce{PbCl2}$ white and $\ce{PbI2}$ yellow $\ce{SnCl2}$ white, $\ce{SnCl4}$ red and $\ce{SnI4}$ black $\ce{AgCl}$ white, $\ce{AgI}$, $\ce{AgBr}$ and $\ce{Ag2CO3}$...
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268 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 ...
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4answers
105 views

Books showing colorful images of elementary particles…is this true? [closed]

Do electrons or protons or any other elementary particle have colors of their own or do they have smell?
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1answer
50 views

The color black [closed]

If a perfectly black object were present and it had a rough texture with bumps and crinkles, would it reflect any light? And can black reflect any light?
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1answer
250 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 ...
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1answer
69 views

why are simple organic molecules usually white?

I have heard that it is because they absorb electronically in the ultraviolet range, if this is true, why is it true. What is it about the nature of organic molecules that make them absorb in the ...
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31 views

How can you reduce Prussian blue without using liquid?

I have Prussian blue, iron(III) hexacyanoferrate(II), pigment suspended in oil, and I understand it is electrochromic; it changes from blue to colorless when Fe(III) is reduced to Fe(II). I've tried ...
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26 views

Why are certain substances clear/invisible? Can we create invisible objects? [duplicate]

This is more so a question of how light interacts with matter. For example, why are substances like oxygen generally invisible? If the light hitting the molecules were absorbed, it would appear black, ...
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0answers
57 views

Why is silver chromate red?

Copper(II) ions are blue and chromate(VI) ions are yellow therefore copper(II) chromate(VI) would turn out to be green because it's a mixture of blue and yellow. In the same way, silver ions are ...
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22 views

What substances are typically used to produce cyan, magenta, and yellow ink?

Early in grade-school you learn blue, red, and yellow are the primary colors that can be used to produce any other color. If you're curious enough, you later learn the primary colors are actually cyan,...
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2answers
312 views

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 ...
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0answers
19 views

Why does some copper (I) compound show color? [duplicate]

As far as I know, if the d orbital of a d-block element is fulfilled, then there is no way for electrons to change the orbital and show color. But some of Copper (I) compounds do show color. How is ...
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1answer
126 views

What are the physical properties of the cation tris(ethylenediamine)cobalt(III)?

I am aware of the (pictured) structure of $\ce{[Co(en)3]^3+}$, but what are the physical properties of this ion? Namely, what is its colour?
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60 views

Do filter-specific dyes exist? Equivalently, do dye-specific filters exist?

Apologies if this isn't chemistry enough for chemistry.se. I'm happy to go elsewhere if there are suggestions. Blue + Red = Purple is arbitrary here. If any different colors might make this more ...
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24 views

Origin of different colour for thio analogue of indigo from blue to red

Why the thio analogue of indigo is red? What is the reason behind change of colour from indigo to red just by change of N to S. What I get is that there will be electronegativity, lone pair ...
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1answer
88 views

How to change color of water based on its acidity?

I recently saw a video on YouTube in which water, when mixed with a solution (I believe iodine was involved,) changed color based on its acidity. I am attempting to replicate this experiment, but ...
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59 views

Chemical reaction , blue to red and again to blue

I am trying to demonstrate color change in the liquid as it passes through a channel. I want the initial color of the liquid to be blue in color and as it passes and comes out of a small pipe , it ...
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63 views

Difference in color between the chromate and permanganate ions

As the title states, I'm wondering why the $\ce{[CrO4]^2-}$ and $\ce{[MnO4]-}$ ions display different colors in solution. Both of the metal ions have a $\mathrm{d}^0$ electron configuration, have the ...