Safety of calcium chloride as a honey desiccant - any chemists out there?

[pargyle]

Wasn't Dun Scotus's original discussion on how many angels could dance on the point of a needle?

Yes I think it was ... but finding that image proved more challenging so I settled on the corrupted version !

 

[jenkinsbrynmair]

Electrolysis
Decomposition of Silver Bromide in sunlight.
Now if you’d said an exothermic chemical reaction Was one that needed energy applied to it I might not have disagreed with you

what about slaking lime (Calcium Oxide) or do you consider the energy needed to carry the bucket of water to it as energy applied?

 

[jenkinsbrynmair]

Yes I think it was ... but finding that image proved more challenging so I settled on the corrupted version !

or maybe it was Thomas Aquinas? always confusing rushing from my A level chemistry class to get a seat by the radiator during scripture classes

 

[pargyle]

or maybe it was Thomas Aquinas? always confusing rushing from my A level chemistry class to get a seat by the radiator during scripture classes

Dun Scotus certainly quoted Thomas Aquinus - A LOT - and progressed the existing theology but ... my theology only came from a friendship with the local curate and usually over a pint or two of Stones bitter in the pub on Saturday night ... so I think I'll leave it at that !

 

[Erichalfbee]

I’m sure Thomas Aquinus had them dancing on the head of a pin?
Is God bound by the physical laws of His universe ( ie. a finite number of angels ) or is He able to transcend his own laws and thereby fit an infinite number of angels on a pin ?

 

[Erichalfbee]

what about slaking lime (Calcium Oxide) or do you consider the energy needed to carry the bucket of water to it as energy applied?

How many joules?

 

[jenkinsbrynmair]

How many joules?

no, just an ordinary two gallon plastic bucket

 

[Erichalfbee]

2 gallons of water is around 10 kg ( I know it’s nearer 9 but ten makes the arithmetic easier)
Lifting that uses 100 joules. How far do you walk?

 

[jenkinsbrynmair]

2 gallons of water is around 10 kg ( I know it’s nearer 9 but ten makes the arithmetic easier)
Lifting that uses 100 joules. How far do you walk?

depends how far away the tap is

 

[jenkinsbrynmair]

of course, if we're working on the old chapel we have no plumbed water (although the village reservoir/tank is next door), so the stream is about forty yards away - unless I use the spring that supplies Tŷ llwyd farm but that's a hundred yards away - downhill

 

[pargyle]

I’m sure Thomas Aquinus had them dancing on the head of a pin?
Is God bound by the physical laws of His universe ( ie. a finite number of angels ) or is He able to transcend his own laws and thereby fit an infinite number of angels on a pin ?

I'll just pop out and ask him ... don't expect an answer any time soon ...

 

[Repwoc]

To save having a competition for who has the last word in this “debate”, it would be helpful for clarification of the terminology which is being used. I used the words “exothermic” and “endothermic” in the context of chemical reactions. I was quite specific in mentioning “chemical reactions”.

If you ask Dr Google for examples, you will find that the melting of an ice-block is described as an endothermic reaction. This is a physical event – the ice will melt if the ambient temperature is greater than the melting point of the ice. Yes, it is an endothermic reaction, caused by the ice absorbing heat from its surrounds, but it is a physical reaction, and not a chemical reaction. No chemical bonds are formed or broken in such a physical reaction. It is true that this can occur at ambient temperatures without generated heat being used, and you can rightly claim that the ice has absorbed heat from its surroundings.

BUT I was specifically talking about chemical reactions which involve chemical bonds being formed or reformed. The following information is from the website:
Simple Endothermic Reaction Examples

Chemical reactions are all about the energy. In an endothermic reaction, heat is used for the reaction to occur. The heat energy breaks the bonds in the substance causing the reaction. As the heat is absorbed, the product will be colder. This is actually one of the key characteristics of an endothermic reaction.

Dani, would you please advise an example of an endothermic chemical reaction which occurs at ambient temperatures in a laboratory?

I think that the website you have quoted is inaccurate or misleading. The thermodynamic terms exothermic and endothermic refer to the enthalpy change of a process (physical or chemical). Processes with a positive enthalpy change are endothermic and those with a negative enthalpy change are exothermic. Endothermic reactions take heat from their surroundings, while exothermic reactions heat up their suroundings.

All chemical reactions require energy to break the chemical bonds of the reactants, including exothermic reactions. It's called the activation energy. Consider the reaction of paper (cellulose) with oxygen. A piece of paper in air will remain unchanged indefinitely at room temperature. However if sufficient activation energy is provided by applying a flame to the paper it will proceed to react with the surrounding oxygen, giving out lots of heat (exothermic). Some of the heat released provides the activation energy for more paper + oxygen to react, until the paper (or oxygen) is exhausted.

The total energy change of a process is the change in Gibbs Free Energy which includes both the enthalpy change and the entropy change x T (absolute temperature). Reactions which involve a large increase in entropy (eg between liquids and/or solids with a gaseous product) may proceed even if they are endothermic. An example is the reaction of sodium bicarbonate with ethanoic (acetic) acid which proceeds rapidly at room temperature releasing carbon dioxide gas while becoming cooler.

 

[drex]

Pardon?

 

[user 20297]

o

Pardon?

I think someone said that some chemical reactions need heat,in order to work, Someone else said that wasn't right. It was corrected, splitting hairs by saying that actually, it's just that heat is absorbed. Then the first person asked for an example of the latter, which someone else provided.

I prefer beekeeping.

 

[jenkinsbrynmair]

Pardon?

a meltdown amongst google experts

 

[user 20297]

a meltdown amongst google experts

 

[jenkinsbrynmair]

I thought you'd enjoy the oxymoron.
or should that be googlemoron!

 

[pargyle]

I thought you'd enjoy the oxymoron.
or should that be googlemoron!

Or just plain moron ?

 

[understanding_bees]

I think that the website you have quoted is inaccurate or misleading. The thermodynamic terms exothermic and endothermic refer to the enthalpy change of a process (physical or chemical). Processes with a positive enthalpy change are endothermic and those with a negative enthalpy change are exothermic. Endothermic reactions take heat from their surroundings, while exothermic reactions heat up their suroundings.

All chemical reactions require energy to break the chemical bonds of the reactants, including exothermic reactions. It's called the activation energy. Consider the reaction of paper (cellulose) with oxygen. A piece of paper in air will remain unchanged indefinitely at room temperature. However if sufficient activation energy is provided by applying a flame to the paper it will proceed to react with the surrounding oxygen, giving out lots of heat (exothermic). Some of the heat released provides the activation energy for more paper + oxygen to react, until the paper (or oxygen) is exhausted.

The total energy change of a process is the change in Gibbs Free Energy which includes both the enthalpy change and the entropy change x T (absolute temperature). Reactions which involve a large increase in entropy (eg between liquids and/or solids with a gaseous product) may proceed even if they are endothermic. An example is the reaction of sodium bicarbonate with ethanoic (acetic) acid which proceeds rapidly at room temperature releasing carbon dioxide gas while becoming cooler.

Thank you, Repwoc, for your explanation.
I would appreciate your comments concerning what possibility there might be for a reaction such as I originally queried, namely:
CaCl2 + H2O => CaO + 2HCl

 

[oliver90owner]

Going back to calcium chloride absorbing water (actually sufficient for it to be termed deliquescent), is that a chemical reaction? I think not in the chemical bonds sense. Initially it is simple hydration - probably only a matter of water of crystallisation and latterly dissolving in the water absorbed. The calcium chloride was solid and is now in solution. Not much of an overall chemical reaction there, methinks? Of course desiccation is carried out before the solution part. The Relative Humidity above a saturated calcium chloride solution is only 35% - so no desiccation at that point.

Have fun in arguing the toss.