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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361 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?
2
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1answer
32 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? ...
4
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0answers
73 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 ...
4
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1answer
54 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 ...
3
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1answer
57 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 ...
4
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0answers
28 views

Increasing Covalent character increases Colour intensity

I observed some trends as follows PbCl2 white and PbI2 yellow SnCl2 white, SnCl4 red and SnI4 black AgCl white, AgI,AgBr and AgCO3 yellow In all these cases as the size of anion increases ( ...
8
votes
2answers
169 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 ...
2
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4answers
97 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
40 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
44 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 ...
5
votes
1answer
58 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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0answers
18 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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0answers
22 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, ...
2
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0answers
31 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 ...
4
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0answers
15 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 ...
10
votes
2answers
94 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
14 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
62 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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0answers
54 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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0answers
16 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 ...
0
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1answer
35 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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vote
0answers
38 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 ...
2
votes
0answers
44 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 ...
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0answers
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what causes the colour change in oscillating reaction? how can i time each oscillation time as accurately as possible? [duplicate]

BZ oscillating reaction this reaction consists of: Potassium Bromate Malonic Acid and Potassium Bromide Cerium Ammonium Nitrate in Sulfuric Acid 0.50% Ferroin Solution I wanted to know where these ...
4
votes
1answer
207 views

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 ...
0
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1answer
38 views

Why is urobilin yellow?

The yellow color of urine is due due a compound known as urochrome, or urobilin. Why is this chemical yellow? There isn't any coordination complexes. What else could cause this color? I have not ...
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1answer
40 views

Is there an agent that changes colour when exposed to air? [closed]

And if so, does it come in a liquid form? Thank you for your time
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1answer
22 views

Spectroscopy and Excitation of Electrons

As metals are heated, they glow white and then blue. How might you explain this change in color as the temperature of the metal is increased? My answer consist of the idea that with increased thermal ...
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0answers
33 views

Looking for an isomerization reaction that involves a color change for classroom demonstration purposes

I am in the process of designing a chemical kinetics course for undergraduates. I would like to demonstrate isomerization equilibria, and therefore am looking for a reaction A <-> B fulfilling the ...
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0answers
75 views

Predict flame test color?

If you know the composition of any sample of compound, is it possible to predict it's flame test color? For eg, if you can given Sodium Chloride, then without actually doing the flame test, can you ...
5
votes
0answers
67 views

Why is NO2 brown?

I have tried hard to find why $\ce{NO2}$ is coloured brown or why any of the coloured gases are coloured but I was not able to find out.
2
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2answers
88 views

Why does oxidized copper become green?

Why does oxidized copper turn green? I am sorry if this question is too basic, but am really stumped here. It would be helpful if one could provide a research paper or website with your answer.
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vote
1answer
122 views

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 ...
3
votes
1answer
215 views

Why do elements change their colour in reactions?

We are almost common with the reaction: $\mathrm {CuSO_4+Fe = FeSO_4+Cu }$. In this reaction initially Copper sulphate is bluish in colour, which gradually changes to pale green. I want to know, why ...
14
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1answer
2k views

Why does water spills on our shirt change its colour?

While drinking water, some of it spilled on my shirt and as usual, as has happened to many of us, the colour darkened. So why does this happen? Is it due to some chemical effect or physical one?
4
votes
1answer
56 views

Is there a way to make long delay ink?

I would like to make some invisible ink that apears by itself after some time, preferably at least a couple of days. I want to write a dedication in a book with it, so it would probably be fine if the ...
12
votes
1answer
373 views

Iron chemistry: acetates for ebonizing wood

I have recently been “brewing” what is commonly called “iron acetate” for ebonizing wood, and I'd like to understand the chemistry of the iron/acetic acid reaction, which should be fairly simple, but ...
11
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1answer
724 views

Why are the plastic balls used to reduce evaporation in this reservoir black instead of white?

Plastic balls have been added to a reservoir in drought stricken California in order to reduce evaporation. (Link to news story here.) Why are the balls colored black instead of white? I would ...
8
votes
1answer
153 views

Why are porphyrins colored when porphyrinogens are colorless?

In heme synthesis, porphyrinogens are colorless but upon their oxidation (from removing 6 hydrogen atoms), they become colored porphyrins. Why does the change in color occur? Is red the only color it ...
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0answers
24 views

What determines the color of a object? [duplicate]

Why is gold yellow for example? Which property of the atom determines the color?
9
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3answers
173 views

Is there a gas with metallic luster?

We know that both solids and liquids can exhibit metallic luster. I wonder whether there is a gas that when filling a transparent envelope (such as a glass tube) would make it appear with metallic ...
3
votes
1answer
280 views

Yellow Color of NaCl

My book says - "NaCl shows metal excess defect, which results into the formation of an F-center in the crystal. This F-center is responsible for the yellow color of NaCl." My question is, how does an ...
15
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2answers
422 views

What color is solid methane?

Is it blueish, perfect white or some other color? I am interested because some celestial bodies are said to be covered with methane ice.
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0answers
45 views

Absorbance of dpph test for antioxidant activity

What is the range absorbance for essential oil sample in dpph test (antioxidant activity)? My absorbance was 1.322. And the inhibition concentration was 21.121. My control absorbance was 1.676. Is ...
4
votes
1answer
61 views

What makes many water soluble fertilizers blue?

I've noticed that water soluble fertilizers tend to be blue. What chemicals or chemical reactions cause this color here? Is this necessary or for aesthetic purposes? I haven't seen this in organic ...
7
votes
1answer
58 views

Is there a known chemical that makes it possible to control the opacity of a large surface?

I have this idea of creating a large domed ceiling/roof for a building that can be made clear to see the actual sky, or made fully opaque/dark grey/black to project an artificial sky onto. I know ...
6
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1answer
75 views

Wavelengths of the visible spectrum

Why is data about wavelengths of different colors and the visible spectrum in general so different in different sources? On Wikipedia, the numbers differ by up to $\pm\mathrm{30~nm}$.
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1answer
671 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 ...
7
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1answer
765 views

What turns clear liquid soap blue?

Liquid soap that sits in metal pump handles turns blue after a week or so, as in this photo comparing the soap in its initial clear state and then after pumping from the dispenser. The pumps are ...
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votes
1answer
307 views

Why are compounds of V5+ and Cr6+ colored?

As far as my knowledge goes, transition metal complex ions show a color due to a transfer of electrons between the levels of split $\mathrm d$-orbitals. In the case of $\ce{V^5+}$ and $\ce{Cr^6+}$ ...