Presentation is loading. Please wait.

Presentation is loading. Please wait.

Post Lab: Electrolytes

Similar presentations

Presentation on theme: "Post Lab: Electrolytes"— Presentation transcript:

1 Post Lab: Electrolytes

2 Electrolytes Are substances that form positive(+) and negative (-) ions in water Conduct an electric current

3 Electrolytes in the Body
Carry messages sent to and from the brain as electrical signals Maintain cellular function with the correct concentrations electrolytes

4 Conduction Illustrated
LED Drop of CaCl2 (aq) Resistor 330 Ω (ohms) Electric current : flow of charged particles. One type of current is electrons flowing through a wire, from cathode (negative electrode) to anode (positive electrode). Another type of current: anions and cations moving through a solution Cations move to the cathode, anions move to the anode. External source of potential (voltage) is required in both cases!

5 Is it a strong electrolyte, a weak electrolyte, or a nonelectrolyte?
Strong electrolytes include: Strong acids (all acids begin with H) Ex: HCl, HBr, HI, HNO3, H2SO4, HClO4) Strong bases (bases end in –OH (Hydroxide) (IA and IIA hydroxides) Ex: NaOH, Ca(OH)2, KOH, Ba(OH)2 Soluble Salts (Most water-soluble ionic compounds) Ex: metal – nonmetal (NaCl) metal - polyatomic ion (Na2SO4 )

6 Strong Electrolytes are 100% ionized
salts H2O 100%ions NaCl(s) Na+(aq) + Cl-(aq) H2O CaBr2(s) Ca2+(aq) + 2Br- (aq) acids H2O HCl(g) H3O+(aq) + Cl-(aq) Bases H2O NaOH(s) Na+(aq) + OH-(aq)

7 Weak electrolytes Most of the solute exists as molecules in solution
Only a few solute particles produce ions HF H2O  H3O+(aq) + F- (aq) acid NH H2O  NH4+(aq) + OH- (aq) base

8 Nonelectrolytes C6H12O6 (s)  C6H12O6 (aq) Dissolve as molecules only
No ions are produced in water Do not conduct an electric current H2O C6H12O6 (s)  C6H12O6 (aq) glucose

9 Electrolytic Properties of Aqueous Solutions
Electrolytes dissociate to produce ions. The more the electrolyte dissociates, the more ions it produces.

10 Dissolving Polar Covalent Compounds Some dissolve only as molecules
EX: Sucrose Dissolves but does not dissociate into ions Timberlake, Page 239

11 * Dissolving Ionic Solutes

12 Solid ionic compounds ~ Ions not free to move not  current ~ Must be dissolved in H2O

13 Observations coming up
Substance tested Scale (0-4) Conductivity ( low, medium, high, none) Strong, Weak or Non-Electrolyte Classification of Electrolyte (acid/base, Ionic salt, alcohol, covalent organic molecule

14 1 C3H7OH Propanol O None Non-electrolyte Large organic molecule 2 KCl (aq) Potassium Chloride 4 Very high strong Soluble Ionic salt 3 H2SO4 (aq) Sulfuric Acid 4 Very High Strong acid 4 H2O Deionized water 1 Low weak Weak acid /base 5 Na2SO4 (aq) Sodium sulfate 6 HCl (aq) Hydrochloric Acid 7 NaOH (aq) Sodium Hydroxide 3 High Strong base 8 C2H5OH2 Ethanol O None (alcohol) 9 Tap water 3 High Acid/base 10 HC2H3O2 Acetic Acid 1 Low- 2 Medium Weak organic acid

15 Ionic equations for each electrolyte
1. C3H7OH 2. KCl (aq) K+(aq) + Cl-(aq) 3. H2SO4 (aq) H+(aq) + SO42-(aq) 4. Deionized H2O(l) H+(aq) + OH-(aq) 5. Na2SO4 (aq) Na+(aq) + SO42-(aq) 6. HCl(aq) H+(aq) + Cl-(aq) 7. NaOH(aq) Na+(aq) + OH-( aq) 8. C2H5OH2 9. Tap H2O(l) H+(aq) + OH-(aq) 10. HC2H3O2 (aq) H+(aq) + C2H3O2- (aq)

16 Questions for Analysis
Some substances conduct electricity because of the ions present. Those substances that do not dissociate into ions do not conduct electricity. Electrolytes=dissociate to produce ions Non-Electrolytes do not have ions to dissociate

17 2. Could any of these substances conduct electricity in the solid form
2. Could any of these substances conduct electricity in the solid form? Explain None of the substances can conduct electricity in the solid form . EX: Ionic compound. When a salt is in a molten state / dissolved in water, the ions can move and carry the electric current. in SOLID STATE= the ions cannot move, so the current cannot flow. COVALENT COMPOUNDS (non metal bonded with non metal), the outer shell electrons are used up to form the covalent bonds. thus, there are no free electrons to conduct electricity. (examples include diamond, PURE water etc) METALS: metals have free electrons which allow them to conduct electricity in both solid and molten state. EX: Copper,steel,water,plasma and most metals conduct electricity in solid form

18 3. Explain some possible reasons for a high conductivity measurement in a freshwater sample from a lake, stream or pond. High concentration of ions (unusual anions and cations) Nutrients (e.g., phosphorus, nitrogen, carbon, silicon, calcium, potassium, magnesium, sulfur, sodium, chloride, iron) are primarily transported to ponds and lakes via streamflow, surface runoff and groundwater,

19 Conclusion An electrolyte is a compound that, in aqueous solution, conducts electricity. As liquids: salts, bases. When aq: salts, acids, bases. When ions are present it can conduct electricity. ex> HCl(aq): H+(aq) + Cl –(aq) NaOH(aq): Na+(aq) + OH–(aq) CuSO4(aq): Cu2+(aq) + SO42–(aq) Nonelectrolytes do not conduct electricity. They do not ionize and therefore have no moveable ions. Acid: a compound that ionizes in water to form hydrogen ions. Base: an ionic hydroxide that dissociates in water to produce hydroxide ions A strong electrolyte has a greater percentage ionization (most molecules are converted to ions).. Weak have a few ions and more molecules so they conduct electricity at a lesser percentage.

20 Conclusion thoughts + + + + + + + Dissociation Na H O H O Cl Cl Na
Dissociation occurs when a (ionic) compound breaks into its ions in water. Ionization occurs when a neutral atom or molecule is converted into an ion (e.g. by water). Ionic compounds and bases dissociate. Acids ionize. Dissociation Na + H O H O Cl Cl Na + + + Ionization + H O H O Cl Cl H + +

21 Sources of error: contamination spilled solution misreading the conductivity apparatus the conductivity apparatus shorts out Not drying off the probes H2SO3: acid, KOH: base, CH3OH: organic, HC3H5O2: acid, Na2C2H3O2: salt, Ba(OH)2: base

Download ppt "Post Lab: Electrolytes"

Similar presentations

Ads by Google