Solutions Review Pt 2 Electrolytes vs Non-electrolytes

Electrolytes vs Non-Electrolytes ElectrolyteNon-Electrolyte When dissolved in water, allows for electron flow When dissolved in water, does not allow for electron flow Produces ions when dissolved in water Does not produce ions when dissolved in water Substances which were formed by ionic bonds Substances which were form by covalent bonds Acids, bases and salts Note: for a substance to conduct electricity, it must be dissolved in water

What’s ionic and covalent again? Ionic bond → bond between a metal and a non- metal – The metal looses electron to get a positive charge – The non-metal gains electron to get a negative charge Covalent bond → bond between non-metal sharing electrons to get stable octet

Electrolyte dissociation Def: electrolytes are dissolved in water, dissociating from one another to their respective positive and negatively charged ions, allowing for conduction of electricity Key thing → get the production of ions during dissociation! – No ions, no electrical conductivity

Examples of electrolyte dissociation Salts NaCl (s) →Na + (aq) + Cl - (aq) CaCl 2(s) →Ca 2+ (aq) + 2Cl - (aq) Acids H 2 SO 4(s) →2H + (aq) + SO 4 2- (aq) HCl (s) →H + (aq) + Cl - (aq) Bases KOH (s) →K + (aq) + OH - (aq) NaOH (s) →Na + (aq) + OH - (aq)

Acids! An acid is a substance that releases H+ ions in an aqueous solution – How can you tell an acid from molecular formula? Usually an acid starts with H atom and is then followed by a non-metal Exception! Acetic acid CH 3 COOH dissociates to H+ andCH 3 COO- Acids rnx with blue litmus paper and turns it red

Bases! A base is a substance that releases OH- ions in an aqueous solution – How can you tell an acid from molecular formula? Usually a base starts with a metal and is ends with OH Exception! Ammonia NH 3 is actually a base even though it doesn’t have an OH- group! – When it reacts with water, the following reaction occurs NH 3 + H 2 O → NH OH- Bases rnx with red litmus paper and turns it blue

Salts! A salt is a substance that is produced by chemical bonding of a metal and a non-metal other than H+ or OH- – It is an ionic bond! NaCl: Sodium chloride dissociates to Na+ and Cl- KBr: Potassium bromide dissociates to K+ and Br- BeS: Beryllium sulfide dissociates to Be 2+ and S 2- Litmus paper has no effect on salts

Types of Electrolytes AcidsBasesSalts DefinitionSub. that when dissociate release H+ in sol. Sub that when dissociate release OH- in sol. When dissociate have metal and non-metal Litmus Paper Test Turns blue paper red Turns red paper blue Does not rnx Uses/Found in Neutralizes base, found in fruits Neutralizes acid, found in blood, cleaning prods Found in fertilizers, soaps, How to recognize Usually starts with H, has H+ gr Usually ends with OH, has OH- gr 1 st = metal 2 nd = non-metal ExamplesHCl, HF, HNO 3 NaOH, Ca(OH) 2 NaCl, AgNO 3 Exceptions to “H” rule Water, Acetic Acid (CH 3 COOH) CH 3 OH, C 2 H 5 0H -> alcohols!; Not bases, NH 9 is a base

pH Scale Used to determine whether or not a substance in solution is an acid, a base, or neutral Goes from 0 to 14 – → acids Strong acids closer to 0 Weak acids near 6.9 – → bases Strong bases closer to 14 Weak bases near 7.1

pH Scale The scale goes up by a 10-fold factor – Meaning if you are comparing an acid with a pH 2 and pH of 3, the acid which has a pH 2 is 10 times stronger – If you are comparing an acid with pH 2 and pH 6, the acid which has pH 2 is 10 4 times stronger

How to i.d if you have an acid, base or neutral substance 1.Litmus Paper Test Tells you if your substance is an acid, base or neutral 2.Buffer Solution + Indicators A buffer solution is a solution composed of a weak acid and it’s associated base. Key: it’s pH changes very little when strong acid/base added to it, meaning it has specific pH levels! An indicator is a chemical which undergoes a colour change at specific pHs

Litmus Paper Test Blue paper – Turns red when introduced to an acid – Stays blue when introduced to a base or a neutral solution Red paper – Turns blue when introduce to a base – Stays red when introduce to an acid or a neutral solution

Buffer Solution + Indicator This procedure plays on the specificity of buffer solutions The first step you do is introduce your solution to the indicator and record that colour Then you introduce your indicator to buffer solutions ranging from pH 1 to pH 14 and match the colour – You may have to use more than one indicator, for their ranges overlap, thus allowing to get a more precise pH value!

pH indicator example pH Thymol Blue Red Yellow Blue Bromo. Blue Yellow Purple Methyl Red Red Yellow Phenol Red Yellow Red Cresol Red Yellow Reddish-Purple Pheno. Colourless Fuchsia Thymol. Colourless Blue

pH indicator example 1.Which indicator(s) would you use to find a strong acid? Strong base? Neutral substance? 2.My solution turned red using Methyl Red and purple using Bromophenol Blue. What’s the pH of my solution (range)? 3.My solution turned blue using Thymol Blue and fuchsia using Phenolphthalein. What’s the pH of my solution (range)?

Mnemonic to remember for acids and bases Acids are red, bases are blue, water is neutral, what about you? Acid → turn blue litmus paper red Bases → turn red litmus paper blue Water → as a neutral substance, does not rnx with litmus paper (same as salts)