Can anyone explain acids and bases to me like I'm an idiot?

[MrsWhattery]

Hi all, posting in Education in the hope of finding some chemistry teachers/experts.

For reasons too dull/potentially outing to go into here I need to understand, and be able to explain, acids and bases, and I have tried using books and google to no avail. I'm scientifically minded and understand most things but I cannot get it. If anyone can answer my questions I would be eternally grateful!

What is confusing me is it seems to have something to do with water. So an acid for example is in water and can be more or less strong, and/or more or less dilute.

So what is an acid, is it a chemical compound (like a salt) or it is some kind of mixture with water (like a salt solution)? If I buy citric acid powder in solid form, is that an acid - and/or how is it different if I add water?

If anyone can simply explain the hydrogen ion aspect too, and why acids and bases are "opposites", but are also somehow on a spectrum, please do!

TIA. It's driving me mad.

Acid has a pH less than 7. Base reacts with acids to form a salt.

An example of a salt is NaCl (Sodium Chloride). The Na (Sodium) is the base. The CL (Chlorine) is the acid.

A salt is an electrically neutral compound formed when cations (positively charged ions) and anions (negatively charged ions) combine through an ionic bond. A classic example is table salt or sodium chloride (NaCl), which consists of positively charged sodium ions (
Na+) and negatively charged chlorine ions (Cl-)

It's something like two atoms meet. Sodium has a positive charge, Chlorine has a negative. They get together and bond, making a crystal, NaCl.

Pop that NaCl in water (H2O) and the atoms get parted making Na and Cl. The Na bonds with an Oxygen and a Hydrogen, the Cl finds a Hydrogen.
What you Have now is NaOH and HCl.

I have a Nobel prize in Chemistry

Thanks - I know that's the case and how PH testing and so on works - but I want to understand what's actually happening and what makes an acid an acid and what it has to do with water. In the same way that I understand, for example, that two H2 molecules plus O2 can rearrange to become 2 x H2O - I can clearly visualise what atoms are involved and what happens and why. But none of the explanations of acids that I have found seem to go into this. Water seems to be involved but it's not clear how.

I'm not sure what it would have to do with water. But an acid will gain electrons, and a base will lose electrons

It's to do with the amount of H+ and OH- ions that a compound splits into when in water.

Water is actually composed of OH- ions and H+ ions which "stick" together due to their opposite charges. There's an equal number of OH- and H+ ions so water is neutral.

Acids release more H+ ions so for example hudrochloric acid (HCl) is actually H+ and Cl- ions. Acids that full break up into their H+ and whichever negative ion it is are known as strong acids whereas ones that don't fully split up are weak acids. This is different to being concentrated or dilute which is how much water is added. So you can have dilute strong acids or concentrated weak acids. The concentration and strength are measures of different things.

Bases are to do with OH- ions for example sodium hydroxide (NaOH) which becomes Na+ and OH- ions. Like with acids these can be strong or weak, and concentrated and dilute.

A chemist might be along to add more/correct but I think that's the basic idea

This any use? www.bbc.co.uk/bitesize/articles/zcnhxbk

All I remember is acids turned ph paper a shade of red and alkalines (bases) turned it purple, but the Bitesize articles are usually pretty good. There are also some very enthusiastic chemistry teachers on Youtube that have helped me with a child who keeps asking questions I can't answer.

Just thinking in H2O, if you look into the molecule it will be charged slightly like H+ and O- so if you wanted to look at it like that you could go as far to say for talking's sake that the hydrogen is the acid and oxygen the base in this situation, but we wouldn't usually describe it in this way because the acid and base combination here would be pretty weak

Acids and bases - Acids and bases - National 5 Chemistry Revision - BBC Bitesize

I lied about the Nobel prize

Or maybe it isn't weak, thinking about it. Hmm

(Vague memory from secondary school science)

I learnt it as acids vs alkali, which I believe that alkali and base are two words for the same thing.

I think it's like a property of a substance, rather than being a thing in itself? So every substance - human sweat, water, apple juice, soap etc - they all have a pH value. We only learnt this about liquids, I'm not sure if solids have a pH value (presumably yes, but they don't really do anything unless they become liquid?)

pH value is on a scale from 1 to 14. With 1 being the most acidic, and 14 being the most alkaline.

7 is neutral. So for example, everything from 1.0 to 6.9 is acidic, but a 5 or 6 is a weak acid, and a 1/2/3 is a strong acid.

Likewise, everything from 7.1 to 14 is alkaline, but a 12-14 pH alkaline is very strong, and an 8 or 9 is weaker.

Water is neutral, so if you dilute acid in water, it will become weaker.

Alkaline and acid can cancel each other out if they are at a similar distance from neutral. So you'd need a pH 6 acid to neutralise a pH 8 alkaline. But a pH 6 acid is not strong enough to neutralise a pH 10 alkaline. You'd need a pH 4 acid for that.

Strong acids and alkalines can be corrosive - e.g. stomach acid, acid used in a lab, acid rain etc.

Weaker acids have a sour taste - vinegar, orange juice are acids.

You can use the acid/alkaline properties of a substance for various uses - for example, toothpaste is alkaline, because it tries to counteract acidic plaque which is excreted in your mouth and can harm your teeth.

Vinegar, as an acid, can be used to clean limescale (which is alkaline) because if you put acid in contact with the lime, it will dissolve it.

Bee stings are acidic but wasp stings are alkaline. So to soothe a wasp sting you want to put a weak acid on it, like cold tea. But if you get stung by a bee you want something alkaline, like baking soda or toothpaste.

Ah sorry I got carried away typing and now I can see that's not really what you're looking for

Well hopefully someone else can explain, as it's past my understanding

YoureTheTop

Apologies, when I responded to your first post for some reason it had only displayed the first line. I can now see the rest of your post! Thanks everyone I'm reading through now.

An acid has positive H+ ions, a base has negative -OH ions. An acid and a base react together to form a salt and water. The water is formed by the H+ ions and the -OH ions joining to form H2O.

Whatever element is attached to the H+ ions in the acid reacts with the element attached to the -OH ions in the base, forming a salt.

For example HCl reacts with NaOH to give NaCl and H2O.

Acid plus base gives a salt plus water.

OK I have some questions if anyone can help!

Water is actually composed of OH- ions and H+ ions which "stick" together due to their opposite charges. There's an equal number of OH- and H+ ions so water is neutral.

This is confusing to me because I thought water was covalent bonding not ionic bonding. Is that right?

*Sodium has a positive charge, Chlorine has a negative. They get together and bond, making a crystal, NaCl.

Pop that NaCl in water (H2O) and the atoms get parted making Na and Cl. The Na bonds with an Oxygen and a Hydrogen, the Cl finds a Hydrogen.
What you Have now is NaOH and HCl.

But that sounds like acid and alkali reacting to make a salt, but in reverse. Does it happen in reverse too? I thought putting salt in water made a solution. Is it actually a reaction with the water forming an acid and a base?

I think it's like a property of a substance, rather than being a thing in itself? So every substance - human sweat, water, apple juice, soap etc - they all have a pH value.

Can anyone confirm this? I thought acids and bases were actual compounds. But then it is true that every substance has a PH, so why is that?

Ow my brain.

An acid has positive H+ ions, a base has negative -OH ions.

But where are these ions? For example citric acid is a compound, it has a molecule. So how does it "have" ions and where are they? I NaCl is made of two ions but it isn't an acid... so what is it about the citric acid that makes it acid? Is it only when it's in water?

All the explanations online talk about ions and reactions but not what an acid or base actually is. Is it a compound molecule? And if so how is its definition as an acid or base all to do with things happening in water? Is the water part of the acid? Is an "acidic liquid" the same thing as an "acid"

I feel like I'm missing some very basic key step in just grasping what it's actually about.

But that sounds like acid and alkali reacting to make a salt, but in reverse. Does it happen in reverse too? I thought putting salt in water made a solution. Is it actually a reaction with the water forming an acid and a base?
You are correct. Acid plus base makes salt and water. You can't (without a lot of energy input) go the other way round.

*Water is actually composed of OH- ions and H+ ions which "stick" together due to their opposite charges. There's an equal number of OH- and H+ ions so water is neutral.

This is confusing to me because I thought water was covalent bonding not ionic bonding. Is that right?*

Right. A tiny amount of water will dissociate. pH is given as -log[H+] so 1x10^-7 moles of water are dissociated in each mole.

I think it's like a property of a substance, rather than being a thing in itself? So every substance - human sweat, water, apple juice, soap etc - they all have a pH value
Im at the edge if my knowledge now....Only things in aqueous solutions have a pH. Alkalis are bases that dissolve in water. Bases react with acids in the same way Alkalis do. I don't know if bases have a pH if they don't dissolve in water.... hopefully this poor answer hasn't confused you more 🤞

1. In terms of the OH- and H+ from water, the H2O molecule is held together by covalent bonds but the molecule "self-dissociates" into H+ and OH- ions. Actually what happens is two molecules react to form H3O+ and OH- ions but to all intents and purposes (especially where acids are concerned) it acts as an H+ ion.

1. I'm not sure about this!

1. Being acidic/basic is a property and being an acid/base is a physical thing. A bit like saying is your sex a property or a thing? Being a woman is a property of who I am but I also am a woman....not sure if that's a helpful analogy! Acids are chemicals that have the property of being acidic. Bases are chemicals that have the property of being basic

Right. A tiny amount of water will dissociate. pH is given as -log[H+] so 1x10^-7 moles of water are dissociated in each mole.

I don't really know what the moles/log part means but do you mean a small proportion of the water molecules separate into H+ and OH- when an acid or base is added? Then what happens?

Yes water is composed of covalently bonded O atoms and H atoms. It's not ionic bonding. It comes down to the charge difference and nature of the substances whether the bond is ionic or covalent. But if you have an negatively charged O- atom and a positively charge H+ atom yes you would separately call them ions.

Yes it can happen in reverse.

Yes it is just the nature of substances rather than a thing in itself.

The ions say in NaCl are like, the Na will have a slight positive charge, there's the ion if you like while the Cl will have a slight negative charge, it's how they're bound together even though the whole NaCl molecule will have an overall neutral, or even, compliment of charges

That's correct about what pp said in water being produced by combining acids and bases, forgot about that

I think what I've said is right, please someone correct me if I'm wrong

No, water - pure water - dissociates very slightly

Also, what makes citric acid an acid is that the whole molecule will have a positive charge rather than neutral

Water is needed for the other compound to dissociate into its ions and "become" an acid.

For example, pure HCl is a gas, hydrogen chloride, that isn't an acid.

When dissolved in water it splits into the H+ and Cl- and is acidic.

Can anyone talk me through an example such as citric acid.

Is the white powder, a solid with a chemical formula, an acid/acidic - or not?

If I dissolve it in whatever, what happens on an atomic/molecular level and what is it about this that makes it an acid? Is the mixture/solution/liquid the acid, or is the acid still just the original citric acid? Why are the ions there, where do they come from, and where do they go? Are they floating around in the solution or boding with something else? When we say an acid can "donate" an ion - what does that mean?

Sorry I'm still not getting it. I hate it because I am used to being able to visualise and grasp concepts and the more I try to get this the harder it seems.

A small amount of water will dissociate regardless of whether there's an acid or base present. In pure water some will be dissociated which gives it a pH of 7