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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Equilibrium constant of water

If $\ce{H2O}$ dissociates as follows: $$\ce{2H2O <=> H3O+ + OH-}$$ and not in this way: $$\ce{H2O <=> H+ + OH-}$$ why is the equilibrium constant: $$K_{eq}=\frac {\ce{[H+][OH-]}} {\ce{[H2O]...
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Determining the formula of tin(II) chloride hydrate [closed]

$\pu{1.20 g}$ of hydrated tin chloride decompose to form $\pu{1.01 g}$ of anhydrous tin chloride on heating. Calculate the value of $x$ given $$\ce{SnCl2.xH2O -> SnCl2 + x H2O}$$ I done it and ...
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What is the ideal temperature and pressure to crack water?

Using sun mirrors and solar cells for electricity. What temperature, pressure and voltage ideal for cracking water. Source: NPR Source Would it take more or less electricity to crack water under ...
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Miscibility of Hexane and Ethanol (Anhydrous vs 96%)

In my lab, I mixed 8:2 (mass:mass) of Hexane:Ethanol (Hexane: 0 ppm of water content, ...
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2answers
624 views

What is the best way to calculate the mass percentage of Calcium Carbonate from water?

Where I live it's believed that local tap water is really bad for drinking because of the amount of limestone. As a science experiment for school I wanted to approximately calculate the percentage of ...
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1answer
646 views

What is wrong with storing deionized water in glass containers?

I have heard that in general storing deionized water in glass bottles is ill advised and that it is better to use plastic. Additionally this is especially important for water used in ICP. I have ...
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2answers
417 views

What is a good source for large tables on the properties of water?

I'm currently doing an investigation for school on finding the Clausius-Clapeyron relation/gradient for boiling water and comparing it to the gradients along my line of best fit. It is given by the ...
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Does mixing calcium dichloride and magnesium sulfate induce a reaction, and how does it affect the hygroscopy of the sample?

I have a problem with a sample made from $\ce{CaCl2*2H2O}$ and $\ce{MgSO4*7H2O}$ in about equal amounts. I took the two salts, pressed them together, and the result was a weird brine that was very wet ...
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Does oxyhydrogen require the presence of water to ignite?

I recently read a short story (fiction) where a major plot element was based on the expectation that a mixture of oxygen and hydrogen will not ignite unless some amount of water is present to get the ...
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1answer
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What is a good resource for learning about the intermolecular bonding in water beyond high school? [closed]

I'm writing a paper for school on boiling water at various temperatures and pressures, but only noting cases wherein high temperatures were achieved without boiling under low pressure (metastable ...
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Does increasing # of hydrogen bonds decrease the strength of these bonds?

I saw the question, "Is the strength of hydrogen bonding greater in hydrogen peroxide or water?" and it made me think of a question on hydrogen bonding: If an oxygen on a water has a ...
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2answers
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Precipitation of AgCl from the tap water solution of the group 2 chloride

I had this question about an experiment where the group 2 chloride was dissolved in distilled water and excess $\ce{AgNO3}$ was added to the solution to form $\ce{AgCl}$ precipitate. One of the sub-...
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Hydrogen Bonding in Water (MO theory)

Valence Bond Theory tells us that each of the “sp3” (in reality, 44% s character) oxygen line pairs in water can act as electron donors, but observing the MO diagram for water tells us that the 2 non-...
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Where does the potential energy of capillary action come from?

Capillary action is when water pulls itself up a paper towel, glass tube or a tree. It is going up, which results in an increase in potential energy. According to the law of conversation of energy, ...
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1answer
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I left a bottle of water in the fridge for the past three months. I took it out today. There was a block of ice in it. How?

How is this even possible? I know my fridge is not freezing items. The bottle was sitting at the back and I totally forgot about it. I went to empty it and heard a clank and noticed there was ice in ...
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224 views

Can running water carry an electrical current indefinitely, and for long distances?

Okay, not a scientist, but doing a writing project that requires a little knowledge. My question is: If there's a constant source generating enough energy into running water (like a stream, surrounded ...
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Why does ice crack when a drink is poured on it?

I think most people have experienced this, but while pouring a beverage over ice I noticed the ice cracked. Before After My initial thought was that because the beverage has an antifreeze property ...
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1answer
141 views

How to show a band structure for water?

This question is generated by my attempt to answer this one. I thought I could demonstrate that electronic conduction in water is possible because of the impact of an electric field on the band ...
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1answer
717 views

H2O and Le Châtelier’s principle [duplicate]

According to Le Châtelier’s principle, the adding of a reactant causes a shift in the direction of products, to minimize the modification. But what about $\ce{H2O}$? When can it be considered as a ...
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Is there any electronic component to water conductivity?

Answers to Decrease in temperature of a aqueous salt solution decreases conductivity indicate that the electrical conductivity of salt solutions arises from the mobility of ionic species and therefore ...
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1answer
127 views

What would be different about a heavy-water ocean world?

The water on Earth is primarily made of $\ce{H2O}$. I'm wondering about the conditions in a hypothetical $\ce{D2O}$ ocean world. Would it be stable over geologic timescales (~$\pu{0.1–2 Ga}$)? What ...
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3answers
902 views

Properties of Water

Water is a substance characterised by properties such as high boiling point and its ability to act as a universal solvent. So why do we say that “the smallest unit of water is a water molecule”? ...
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4k views

What is the real pKa of water?

What is the $\text{p}K_\text{a}$ of water? A simple google search yields the value $15.74$, but this site and this paper say it's $14.0$. According to my understanding, the correct answer should be $...
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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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Is there any difference between thermal energy at room temperature in fluids(water) vs air?

Context of the question: I was reading on hydrogen bonds, specifically how close they are to the thermal energy of the fluids. So I googled the value of thermal energy at room temperature, which was $\...
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Electrolysis in water with baking soda

Many demonstrations of electrolysis show the use of baking soda and a 9 volt battery for electrolysis of water. As a science experiment, I tested different voltages by adding more batteries. In my ...
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Urea + water yields … urea + water?

I added urea to water and, predictably, observed a temperature drop (10 C). I wanted to place the beaker under (reasonably) high vacuum (for a classroom) and recover the urea as a dry substance. ...
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Isotopes of Elements

When we talk about the substance $\ce{H2O}$ with a molar mass of $\pu{18.0 g/mol}$, what hydrogen and oxygen isotopes are present in the $\ce{H2O}$ molecules? In other words, what isotopes do the ...
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Could Na+ ions in water used with a humidifier cause dust everywhere?

We have very dry air in our small family house. So we bought a humidifier ( https://www.klarstein.com/All-products/Monaco-Digital-Ultrasound-Humidifier-White.html ) But here comes the issue: the ...
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1answer
86 views

Which component in my tap water “scale” does not react with acid?

Where I live we have pretty hard tap water and so I'm used to scale build-up in kettles and on bathroom tiles, easily removed with acids (it's mostly calcium carbonate I guess). However it seems a ...
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2answers
689 views

Chemical composition of seawater

Is it true that the sea water is composed of about $86\%$ oxygen, $11\%$ hydrogen and $3\%$ of minerals? The chemical formula of water is $\ce{H2O}$ (two hydrogen and one oxgen) that shows that the ...
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1answer
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Water as a “Harmful Acid”

Apologies for the question which is far below the brilliance of the minds on this page. I have an A-Level in Organic Chemistry but I'm tying myself in knots with this one. I'm a magician looking to ...
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1answer
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What is a simple formula to approximate the change in relative humidity as temperature rises/falls?

The moisture-carrying ability of air goes up as the temperature rises. So if I take a volume of air and heat it or cool it (allowing it to expand/contract so the pressure remains constant) how can I ...
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1answer
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Oxygen Solubility in Water

This is probably really obvious, but I really don't understand. Why does oxygen dissolve in water when oxygen is a nonpolar molecule and water is a polar molecule? It's obvious that oxygen does ...
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1answer
538 views

Is the water in an aqueous solution undergoing a reaction considered part of the system or surroundings?

System: In chemistry, a system is a chemical reaction. A system operates within its surroundings. Energy can move between the two. Surroundings: The environment around a particular chemical reaction....
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1answer
168 views

Calculating the standard reduction potential for the oxidation of water

I was working with Latimer and Frost diagrams for oxygen when I came across what seems to me a contradiction. From the Latimer diagram for oxygen below, we know the standard reduction potential for ...
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0answers
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Is there a non toxic moisture indicator that can be applied on a wall?

I am looking for a substance that could serve as an indicator for a risk of mold growth, e.g. by a change of its hue. Cobalt chloride is both irritant and carcinogenic so is not an option. I've found ...
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1answer
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Does coffee have the ability to dissolve less sugar into it than water?

Like water can absorb such and such an amount of sugar, can coffee absorb less as it already has coffee in it.
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6k views

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
89 views

Turning hot water to cold water [closed]

Is there a way to turn hot water instantly to cold water? Is there some sort of chemical reaction or element that allows this process to happen?
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1answer
36 views

Would atomic oxygen and atomic hydrogen result in O2 and H2 only, or some H2O too? [closed]

Let's assume we have atomic oxygen and atomic hydrogen in a closed chamber, the temperature and pressure of which we're able to monitor (and control). Number of hydrogen atoms are twice that of oxygen....
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2answers
582 views

Converting Chlorine Dioxide concentration to Chlorine

Looking for a little guidance. I have been given some water quality data as part of a project. Specifically I'm interested in the concentration of Chlorine in river water. The analysis results ...
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1answer
467 views

What component(s) of instant coffee make it deliquescent?

If I put small, separate piles of instant black coffee powder, sugar, powdered creamer, and even something very ionic like table salt out in humid air and come back in a few days, only the instant ...
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1answer
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Can ideal gas law be applied to water vapour? [closed]

How to accurately estimate the molar concentration of pure water vapour at 298 K? Can ideal gas law be applied to water vapour to calculate the molar concentration?
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1answer
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Is the relative humidity of pure water vapour 100%?

If there is pure water vapour in the gas phase, can the partial pressure be taken to be equal to the vapour pressure of water at that particular temperature? edit: How is relative humidity calculated ...
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1answer
2k views

Diluting methanol in water: is it exothermic?

Can someone explain in simple terms why does temperature increase when mixing water with methanol? I do not have a strong background in chemistry, but I usually have to mix both liquids (sometimes ...
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1answer
2k views

Hygroscopic Substances and Drying Agents

My book says: Most of the hygroscopic substances are drying agents Based on what I read on several websites, I think dehydrating agents also act as drying agents. If so, all dehydrating agents ...
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1answer
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Mechanism of Water Potential

The idea of water potential still confuses me. I understand the general idea: water moves from an area of higher water potential to an area of lower water potential. However, I still do not understand ...
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1answer
69 views

Understanding water models?

I generally work on fluid flow, so some basic concepts in chemistry are new to me. Work I'm doing requires use of molecular dynamics (MD) to do classical potential simulations of water–NaCl systems ...
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1answer
980 views

Which chemical could be used to decrease water boiling point to a minimum possible level without heating it [closed]

I aim to decrease boiling point of water that will be used to generate steam. I wonder maybe there is an opportunity to add a substance that will help to decrease boiling point of water without ...

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