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Physical Science Notes 416-436
pH
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A very pHun part of chemistry

pH scale

 

What is the pH scale:

 

The pH scale tells you if something is a Acid, Neutral (Salt) or a Base by using a colour/ number scale.

phscale.jpg

Understanding pH

 

To understand pH you need to know about ions.

ions.jpg

*ions are charged atoms.

 

There are 2 types of ions:

 

1)      + ions = CATIONS

2)    --  ions = ANIONS

 

A bit about cations:

 

-         + --> go towards the cathode (negatively charged)

-         Cathode = Negative electrode (CRT, see Atomic Theories page)

 

A bit about anions:

 

-         go towards the anode (positively charged)

-         Anode = Positive electrode (CRT, see Atomic Theories page)

 

How metals are affected:

 

Metals = lose e- ---> + ions

 

            Groups 1A = 1 valence electron ---> lose 1 electron ---> +1

            Gr. 2A = 2 val e- ---> lose 2 e- ---> +2

            Gr. 3A = 3 val e- ---> lose 3 e- ---> +3

                                                                 ions

 

How nonmetals are affected:

 

Nonmetals = gain e- ---> - ions

 

            Gr. 5A = 5 val e- ---> gain 3 e- ---> -3

            Gr. 6A = 6 val e- ---> gain 2 e- ---> -2

            Gr. 7A = 7 val e- ---> gain 1 e- ---> -1

                                                                  ions

 

HOH   ---> H+   +   OH-

                 (+cat)    (-anion)

abs.jpg

ABS

 

A (acids) ---> form H+ ions in water

 

B (bases) ---> form OH- ions in water

 

S (salts) ---> form +ve metal ions

                        -ve nonmetal ions

 

Electrolytes:

 

An electrolyte is a chemical  wich conducts electricity in water because it produces ions in water

The types of chemicals that do that are: ABS (Acides, Bases,Salts)

 

Antacids

 

What do antacids do

 

An antacid neutralizes an acid.

 

How do you neutralize an acid

 

There are two ways to neutralize an acid:           1) Use a base (metal OH)

                                                                        2) Use a carbonate (H CO3)

 

1) Base:

            Mg(OH)2 ---> Milk of magnesia

            (m-OH)                 (m.o.m)

 

e.g.: HCl + Mg(OH)2 ---> MgCl + H2O

      (Acid) + (Base)    ---> (Salt) + (Water)

 

2) Carbonate:

            CaCO3   or   NaHCO3

Other examples of carbonates: 

-Limestone

-Pearls

-Shells

-Eggshells

-Chalk

-Marble

-Tums for your tummy = CaCO3

 

            2 HCl + CaCO3 ---> CO2 + CaCl2 + H2O

            (Acid) + (Carb.) --->(CO2)+(Salt)+(Water)

 

Any Acid + Carbonate = CO2(g) + Salt + Water

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