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Copy of Acids and Bases

Level 1 Science
by

Sally Graves

on 1 March 2013

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Transcript of Copy of Acids and Bases

Substance Reaction in: Universal Litmus acid or base? HCl
Hydrochloric acid NaOH
Sodium hydroxide CH COOH
Acetic acid NH OH
Ammonium hydroxide H O
Water Ca(OH)
Calcium hydroxide 3 4 2 2 + HCl MgCO 3 → Hydrogen carbonates = HCO e.g. Zinc hydrogen carbonate = What about Phosphorus?
Protons =
Electrons =
Neutrons = 1 0 1 Nucleus Outside Nucleus neutral -ve +ve Neutrons Electrons Protons The building blocks of all matter. 26 1 Mg H Magnesium Iron Mass no. Name Symbol Atomic no. Substance made up of only 1 type of atom. ELEMENTS Page 15-16 (13-14)
Groups (column on PT) share similar reactivity...
because they have same # valence electrons.
As you go down a group the reactivity increases.
What group are these in: Lithium, Iron, Nitrogen?
Name 3 elements in group 2. 2, 8, 2 8 e 8 e 2 e In shells around the nucleus. ELECTRON ARRANGEMENT B The Mass Number:
= protons + neutrons The Atomic Number:
= protons
= electrons WHAT IT MEANS 5 11 Page 14 (12) 15 15 16 So for Boron…
Protons =
Electrons =
Neutrons = 5.811 5 5 Superscript is used for ion charges An atom that has gained or lost electrons... IONS Try: copper sulfide silver nitrate sodium oxide subscript The compound formed will be will be attracted to IONIC COMPOUNDS The brackets are needed to show that we want 2 of the whole thing. So for each Mg we will need 2 Nitrates: Magnesium Nitrate DIFFICULT ONES Only required for Excellence?
Balance product and reactant so no atoms are vanishing or created. BALANCING EQUATIONS A reaction is Reactants → Products
  _____ + _____ → ______ + _______  CHEMICAL REACTIONS Sound RATES OF REACTION  
 
 
  COLLISION THEORY Particles inside cannot Particles on surface can react Pain in the stomach is often caused by excess acid and this can be relieved when magnesium hydroxide neutralises the acid. Tablets of magnesium hydroxide are sold for this purpose. How would you obtain the quickest relief from pain? Explain your answer fully.  SURFACE AREA If a solid broken up, the surface area of the sample is increased (more particles are exposed), so the rate of reaction is increased.  CONCENTRATION As the concentration of a solution increases there are more particles so more collisions will occur between reacting particles.   TEMPERATURE When temperature is increased the particles gain kinetic energy. This means that... CATALYSTS A catalyst lowers the energy required to have an effective collision, but is not used during the reaction. Beryllium hydrogen carbonate Be(HCO ) Magnesium carbonate MgCO Nitric acid HNO Acids can best be described as H+ donators. Ammonium hydroxide NH OH Sodium oxide Na O Hydrochloric acid HCl Sulphuric acid H SO Can be identified using indicators. 2 common types: ACIDS AND BASES BASE Purple Blue NEUTRAL Green Blue Red BASE BASE ACID ACID Blue Blue Blue Blue Red Red Orange Red Using small samples of the universal and litmus indicators, find out if the following are acidic, basic, or neutral. INDICATORS STRENGTH Some acids and bases break up in solution easily, e.g. HCl → H + Cl THE pH SCALE ALKALIS Bases that dissolve in water are called alkalis.
It is difficult to test the pH of bases that do not dissolve in water. An example:
Copper oxide reacts with sulfuric acid to produce a blue substance with a neutral pH, which crystallises when the water is evaporated. Symbol equation: Word equation: General equation: H O + CuSO + H SO CuO Water + Copper sulfate + Sulfuric acid Copper oxide Water a.k.a: acid + base…
Acid + Base → metal salt + water METAL OXIDES or HYDROXIDES + ACID + Acid + Salt Metal oxide (or hydroxide) An example:
Magnesium carbonate fizzes with hydrochloric acid. The gas produced turns limewater milky and the remaining solution can be evaporated to leave white crystals. 2 + CO Carbon dioxide + CO Symbol equation: Word equation: General equation: H O + MgCl Water + Magnesium + chloride Hydrochloric acid Magnesium + carbonate Water + Salt + Acid Carbonates = CO e.g. Magnesium Carbonate = METAL (HYDROGEN) CARBONATE + ACID Metal carbonate CHEMISTRY ACIDS AND BASES 4 credits External ATOMS An atom is made up of smaller bits called… Periodic table: Why is the mass number weird? The number of neutrons can vary. These variants are called isotopes. The mass number is the average mass. So the electron shell for Mg would be… Shell 3 holds Shell 2 holds Shell 1 holds Be S Cl Ar C What ions will these atoms become?: - Now has 10 electrons, 12 protons. The ion is Electrons 2, 8, 2 e.g. for Mg: ...and become more stable. ...to get a full outer (valence) shell... loses outer 2 Mg 2+ Anion first, cation second Mg 2+ Cl - Forms an ionic lattice. Balance the + and – so there is no charge. e.g. Magnesium chloride each Mg will attract 2 Cl’s Mg 2+ Cl - Mg 2 Cl NO 3 - SO 4 2- CO 3 2- HCO 3 - NO 3 - Mg 2+ Mg 2+ NO 3 - NO 3 - Mg(NO ) 3 2 Try: ammonium sulfide, iron(III) hydroxide, aluminium sulfate Iron + Oxygen → Iron (III) oxide K O + HCl → KCl + H O Na + HCl → NaCl + H Try: Fix: 2H + O → 2H O Not balanced: started with 2 O’s and ended with 1 O. E.g. H + O  → H O NOTE: Never (ever) mess with the chemical formulae (ever) (this will affect your Merit chances). e.g. Add 1cm Mg to 2cm HCl in a test tube obs: Mg disappeared, gas produced (H ), temp increases Equation: Mg + HCl → H + MgCl e.g. Add 2cm NaOH to 2cm CuSO in a test tube obs: changes colour, solid formed Equation: NaOH + CuSO → Na SO + Cu(OH) Equation: Mg + O → MgO obs: Mg disappeared, bright light, white powder formed e.g. Burn 3cm Mg ribbon by igniting with a bunsen REACTION OBSERVATIONS Some reactions are fast (Mg + HCl) and some are slow (Fe + O2). The rate of a chemical reaction describes how fast a reaction is. Rate can be measured by finding out: - how fast a reactant is used up, or - how fast a product is formed e.g. Mg + HCl → MgCl2 + H2(gas) How could we measure the rate? The faster H2 (bubbles) are produced, the faster the reaction. The faster the Mg is used, the faster the reaction. The higher the temperature? The sound it makes? The conductivity (= saltiness) of the solution? The pH decrease?  A reaction occurs when particles collide… …with enough energy to break bonds between reactants. ...in the correct orientation... The more frequently effective collisions occur, the faster the rate of reaction. Factors affecting the rate of reaction: surface area (of solids) concentration (of solutions) temperature catalysts ...they move faster so have more collisions... ...they have more energy so are more effective. Stirring to dissolve a solid in a liquid increases the surface area of contact so the rate of dissolving increases.  CO 2 2 2 2 2 2 2 2 2 2 2 4 2 2 4 4 2 Chemical reactions are noticeable due to changes (some or all of): Reactants disappearing Products appearing Flame Smoke Gas production Colour change Temperature (increase or decrease) Page 10 (8) Page 11-12 (9-10) Page 17-18#1,4 (15-16#1,4) Page 19, 23 (17, 21) This involves cations (+), anions (-), and an ionic bond between them NAMING Cation ends in -ide... ...except cations with lots of O’s (end in –ate), like these: WRITING FORMULAE Page 23 (21) Page 24-5 (22-3) Page 26-9 (24-7) Page 26-7c, f... (24-5c,f...) e.g. a sample of air contains about 20% oxygen gas. So a reaction done in air will generally be slower than the same reaction done in oxygen. In oxygen there are more effective collisions. 2 Carbon Dioxide gas (CO ) is colourless, odourless, more dense than air and basic. How do we test for it? It turns limewater milky In a test tube add 2 mL (about 2cm) of HCl, and add a limestone chip (CaCO ). Bubble into limewater using a collection tube and observe over a couple of minutes. 2 3 Bases are H+ acceptors (they react with acids to make water and a salt). 2 4 3 2 4 3 3 2 Acids you must know: Base examples: Universal indicator Litmus (paper or solution) + - These are strong acids, as there are lots of H ions. Weak acids don’t break up easily, so there are few H ions. + + → → → 2 4 2 4 3 2- 3 - Metal (hydrogen) carbonate + acid → H O + metal salt + CO (all neutral) 2 2 → → 2 2 2 2 MgCO 3 Zn(HCO ) 3 2 Review questions: Page 36 (34) Expt page 44 (42) Expt page 40 (38) Expt page 42 (44) Expt page 45 (43) Page 37 (35) Rates: 48-51 (50-53) Foundation: 32-3 (30-1) Equations 55 (53) Page 56 (54)#7-8, 57 (55)#1,3,6 Page 58 (56) pH OF HOUSEHOLD SUBSTANCES Carry out the experiment on Page 59 (57) with:
Vinegar
Hair remover
Deodorant
Fly spray
Baking powder
Baking soda NEUTRALISATION The reactions you need to know about this year are neutralisation reactions. This means that they involve reacting an acid and a base to get neutral products. Since there are only 3 acids that you will get asked about, there are only 3 sorts of salts you can produce: Hydrochloric acid Nitric acid Sulfuric acid Acid Ion produced Salts formed NO SO Cl 3 4 - 2- - nitrate sulfate chloride Page 64-5 (62-3) Page 69 (67) Acids and Bases: 74-5 (76-7) Practice paper: 76-81 (74-9) Acid + base: page 66 (64) Acid + carb: 70 (68) Balancing page 66 (64) Balancing page 70 (68)
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