Questions tagged [water]

For questions relating to water (H₂O), specifically its structure, properties, and uses in chemistry. For questions not about water but rather about solutions in water, use tags [aqueous-solution] or [solubility] instead.

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31 views

How to dissolve magnesium malate in water?

When I mix magnesium citrate with hot water, it quickly dissolves and the water becomes transparent. When I do the same with magnesim malate, it does not dissolve, it sinks to the bottom as sand. ...
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3answers
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Can you make deuterium-depleted water through a freezing method?

Deuterium-depleted water (DDW) is sold commercially by some companies. It is apparently manufactured by fractional distillation, which leverages differences in boiling points of heavy and light water. ...
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Lowering water hardness using Ion exchange method [closed]

I want to remove water hardness using Ion exchange resin filter. Does anyone tried this method I want to know if this method really lowers the hardness. What is the best method of regenerating resin ...
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Ionic Product of Water

Why is the ionic product for water ($K_\text{w}$) temperature dependent? The concentration of $\ce{H+}$ and $\ce{OH-}$ ions in pure water is $[\ce{H+}] = [\ce{OH-}] = 1.0\times 10^{-7}\ \mathrm{mol/l}$...
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What is the value of dissociation constant of water at 25°C

According to my class notes, $$ K_{dissociation} = \frac {[H^+][OH^-]}{[H_2 O]} $$ $$ = \frac {10^{-14} }{55.55} $$ $$ = 1.8 * 10^{-16} $$ But shouldn't we ignore concentration of water (55.55 M) as ...
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817 views

Why is ice cubical in structure at very low temperature?

My book says that at atmospheric pressure ice crystallises in the hexagonal form but at very low temperatures it condenses to cubic form. Why and how does this happen?
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How was the ionization constant of water found? [closed]

We were just starting to learn about pH in school recently and we learned that $K_w$ is a constant at $\pu{298 K}$ and it's equal to $10^{-14}$, the teacher said this could be found experimentally but ...
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Is there a chemical that when added to water makes the water flash evaporate?

Im wondering if there is a chemical that you can add to water that will make it evaporate extremely fast, either by raising the temperature of the mix or some other method.
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1answer
239 views

Solar still and how it works

I use a solar still that holds 182 cubic feet of water. Here is how it works: There is an insulator on both sides of the metal bowl. On the outside it covers the whole thing. on the inside it covers ...
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1answer
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Concentrating mixtures of volatile compounds

My interest is primarily food-related here but I think this is a fairly general chemistry question. Let's say I took some liquid like lemon juice and ran it though a rotary evaporator to get just the ...
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2answers
70 views

What happens to the crystal structure of ice as it gets colder and colder [duplicate]

Not sure if this belongs on Chemistry or Physics stackexcahnge. As water freezes into ice, it turns into a solid, and expands as it forms a crystal structure. But what happens to this crystal ...
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What is the essential difference between distilled water of different distillation levels? [closed]

Although not a chemist I often read that different liquids made of molecules with enough low molecular weight and enough strong chemical bonds can be distilled by this process: The liquid (say, water)...
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Density of water increases from 273 to 277 K due to increase in entropy?

In a set of questions that I was solving, the answer to one of the questions asking why the density of liquid water increases from 0 to 4 degrees C had the above answer: due to an increase in entropy. ...
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Will charcoal briquettes (not activated) absorb water out of the air in the house in a subtropical climate?

I live in Florida, an incredibly wet environment where it's very difficult to get moisture out of house without using a dehumidifier 24/7, which is too expensive. Would charcoal briquettes be of any ...
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Figure out how many deuterium atoms in a 3 microgram ice core sample

I'm in an introductory Chemistry class and ran into a Pearson problem, that no-one in our class including our professor has been able to truly figure out. I know the solution is $4.69 \times 10^{13}$...
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Why does humidifier put measurable PM2.5 in the air?

(I know little science so please help me if I'm in the wrong place or if my question needs editing. I could use help with tagging, for example.) I use two devices that measure PM2.5: Kaiterra ...
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1answer
33 views

What causes the differences in price in home testing kits for lead in water? [closed]

The price differences between home testing kits to test tap-water for lead are huge. 20 dollar will either buy 1 test kit or 100 test strips. Both are intended to test drinking-water safety. What ...
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1answer
54 views

Ventilating combustion byproducts in water heaters

I'm designing a system which will heat up water by burning natural gas which is commonly available. I would like to have a slow flame because water will need to reach $\mathrm{70^\circ C}$ and stay ...
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4answers
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Why is oxygenated water not H2O2?

Oxygenated water has become popular for a variety of uses recently - for health purposes internally as well as enhanced wound healing. Anyhow, my dad asked me recently if I knew how it is that ...
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3answers
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Tap water pH adjustment using citric acid

I've lowered tap water pH from 7 to 6 using citric acid. After couple of hours pH raised again to 7. What is the reason for this raise? Citric acid overcomes waters buffering feature then raise the $...
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Is pure water very corrosive?

In other site, someone claimed that pure water is very corrosive. Water distilled for some laboratory uses (like the Z-pinch reactor) is distilled to 0.00000009% purity, and is caustic enough to ...
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Equation of water at triple point

I was thinking about what exactly happens at the triple point of water, and what could be the effect of adding solutes/solvents. I feel we can represent the triple point using the following ...
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2answers
46 views

Does ice increase the humidity of its surroundings? [closed]

Does ice increase the humidity of its surroundings? I'm trying to use the BME280 for an Arduino project regarding locating ice, but I don't know whether the atmosphere is more humid around ice. I'm ...
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Is it more energy efficient to desalinate seawater by flash boiling or by flash freezing? [closed]

In Saudi Arabia I think there are two types of desalination using flash boiling from electric power production and also from flash freezing using solar absorption refrigerant freezing. One requires ...
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What might serve as an initial starting photocatalyst for this large water-splitting solar simulator?

Question: What might serve as an initial starting photocatalyst for this large water-splitting solar simulator? Surely there must have been some planned experiments! The Gizmodo article Insane Light ...
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Why is ammonia less acidic than terminal alkynes?

Here's a picture from Organic Chemistry by Solomons, Fryhle & Snyder : Why is it that ammonia is less acidic than terminal alkynes even though water, and even alcohols, are more acidic than them?...
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Using charcoal to clean water [closed]

I have read about charcoal being used to clean water before it is then boiled or mixed with a UV light stick. I have some questions about this: 1) Does it have to be activated charcoal? 2) Can ...
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2answers
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Is there a treatment for distilled water to become drinkable? [closed]

It is my understanding that, drinking distilled water may not be recommended. Its not recommended indeed. Or maybe its not not recommended... Maybe not not indeed........ Anyway.... Well, apparently, ...
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Electrolysis of water and Gibbs Energy

I'm writing a chemical equilibrium program which minimizes the Gibbs energy. The program accepts as input the total amounts of the elements comprising the system, and a list of possible molecular ...
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Is the equation pH + pOH = 14 valid at different temperatures?

$\mathrm{pH} + \mathrm{pOH} = 14$ For water at 60 degrees Celsius, $K_\mathrm{w} = 1 \times 10^{-13} = [\ce{H+}] \times [\ce{OH-}]$ Hence, $[\ce{H+}] = 1 \times 10^{-6.5} = [\ce{OH-}]$ So $\...
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1answer
39 views

Is there a temperature where salt doesn't dissolve in water?

I know that salt dissolving in water is driven mostly by entropy. However, at lower temperatures, entropy is less of a factor in controlling reactions. Is there a temperature where salt doesn't ...
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2answers
81 views

Does water in big cities get heated (boiled) for treatment?

I live in Bangkok and read how water comes to customers here: I understand from the chart that water go through Thon Buri treatment plant (west Bangkok) and Mahasawat treatment plant (east Bangkok) ...
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5answers
291 views

Numerical related to crystallisation of water below its freezing point

Question: There is $16\ \mathrm g$ of pure water in a container at temperature $-20\ \mathrm{^\circ C}$. A small piece of ice is added to start crystallization. Amount of water in container when ...
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Why is a tin can that appears like galvanised steel rusting?

I bought a canned pineapple and finished the content. The part of the can that is in contact with the liquid appears like galvanized steel (crystalline surface or spangles sort of appearance), while ...
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1answer
210 views

How do I convert this ion exchange capacity into water softening capacity?

I am researching for an extended experimental investigation into methods of water softening. One such method is the use of ion exchange resin. I have contacted the supplier of the resin for its ...
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1answer
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How does ice melt?

I know that when water freezes, it forms a crystalline structure created by the hydrogen bonds between polar water molecules. Also, I know that during a phase change, the potential energy of the ...
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Is there a simple field test for heavy water?

Thought experiment Given two glasses of water, how would one detect which glass contains heavy water, and which contains potable water without using complicated laboratory equipment? Something like ...
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What formula allows adjusting balance of (Ethyl Alcohol / Water / Caffeine powder) to know concentration for the Caffeine solution?

I am experimenting with different levels of concentrated caffeine solution. The solution has a small percentage of ethyl alcohol, in the $\ce{H2O}$. Problems encountered too much ethyl alcohol ...
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1answer
688 views

Can water volume reduce with introduction of another chemical [duplicate]

Can a chemical be introduced to a volume of water which can actually reduce the volume of water in that container?
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If electrolysis splits water, why does only either hydrogen or oxygen (but not both) bubble up on one pole?

If electrolysis splits water, then that means that $\ce{H2O}$ is split into $\ce{H}$ and $\ce{OH}$ or $\ce{O}$. How come that if a water molecule is split at e.g. the negative pole (anode), only the ...
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Why does pKw first decrease but eventually increase when temperature rises?

I understand the initial decrease in pKw. $\ce{Heat + H2O (l) <=> H+ (aq) + OH- (aq)}$ Temperature increases, reaction shifts to the right, so $\ce{H+} \text{ and } \ce{OH}$ ...
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1answer
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Copper wire smoking underwater [closed]

I am doing an electrolysis experiment with two copper wires inside of test tubes that are both submerged underwater, with 20 V per wire. Test tube A is creating oxygen gas at a high rate, but test ...
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Method to find out the amount of solvent replaced by another solvent

So I am performing a relatively simple coprecipitation experiment to synthesize ceramics. All my precursors are in aqueous solutions. But due to the high surface tension of water, drying the water is ...
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Thermal decomposition of steam to hydrogen and oxygen; at what temperature is half decomposed and how to calculate?

In comments below this answer in Space Exploration SE I've said: (Wikipedia) says that dissociating water costs about 4.4 eV per bond. If 𝑘𝐵𝑇= 4.4 eV and $k_B$ is 8.617E-05 eV/K then that ...
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4answers
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When our hard water is boiled, it leaves a blue-green residue in our kettle.

The inside of our kettle is lined in a blue-green deposit. Our water is very hard, but what minerals could cause the coloration?
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Ionic content of different samples of water

So I was reading about impurities of in water and I have a question in mind: So say we have Distilled Water , Deionized Water , Tap Water and Soft water which was softening using dowex resin or any ...
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Does the electrolysis of water produce chlorine gas?

http://orbitingfrog.com/2014/11/02/electrolysis-of-water-with-pencils-and-a-9v-battery/ This article seems to indicate that "a small amount of Chlorine may be produced as you [perform electrolysis on ...
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Is there a food-safe hydrophobic liquid with a substanially higher density than water?

Requirements In short, I am looking for a fluid that meets these criteria: Hydrophobic Denser than water Low viscosity Food safe Background We are working on adding a pool and designing a backyard ...
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Would sodium explode in salt water?

I’ve seen the video etc of sodium being put into freshwater and the reaction of flames/small explosion but I wonder if the same reaction would occur if conducted in salt water such as the ocean.
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Precipitation of water-insoluble materials from shower or laundry greywater

I am currently working on a project to build a filter that aims to separate or salt out the 'dirt' in shower or laundry greywater. The ideal result from this chemical reaction will be such that the '...

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