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Displacement Reactions

Displacement Reactions. Single Displacement Reactions. Single Displacement reaction: A chemical reaction in which an element takes the place of (displaces) another element in a compound. A + BC AC + B (where A & B are metals).

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Displacement Reactions

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  1. Displacement Reactions

  2. Single Displacement Reactions • Single Displacement reaction: A chemical reaction in which an element takes the place of (displaces) another element in a compound • A + BC AC + B (where A & B are metals) • A + BC BA + C (where A & C are non-metals) + +

  3. Displacing Metals With Metals • When a piece of copper is placed into silver nitrate, metallic silver ions form on the copper • The solution turns blue because copper atoms from the wire dissolve in solution and displaces the silver from the silver nitrate compound Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)

  4. Displacing Metals With Metals • In this reaction a metal (copper) replaces another metal (silver) • Or, a positive ion (Cu2+) replaced another positive ion (Ag3+) Cu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)

  5. The Activity Series • By trying different combinations of metals and compounds, scientists have arranged the metals according to their reactivity • The activity series is a list of elements ranked according to their chemical reactivity • Most reactive is at the top, least at the bottom An element can only displace another if it is below it on the activity series!!

  6. The Activity Series • Hydrogen is the only non-metal in the series • Since hydrogen ions can be positively charged, metals can replace hydrogen in compounds • In these reactions, hydrogen gas H2(g) is formed • Metals above hydrogen can replace hydrogen from an acid, metals below hydrogen cannot What do you get when you place Zn in HCl?

  7. The Activity Series • An example of Zinc (Zn) displacing hydrogen gas from hydrochloric acid (HCl) Zn(s) + 2HCl (aq) ZnCl2(aq) + H2(g)

  8. Sample Problem: The Activity Series • Use the activity series to predict if the following reaction will occur. If not, indicate “NR” for “No Reaction”. If so, complete and balance the chemical equation Al(s) + CuI2(aq)

  9. Sample Problem: The Activity Series • Aluminum will replace copper • Aluminum becomes Al3+ and the bromide ion remains Br- • To be neutral, the new compound must be CuBr2 • As a pure element Cu(s) has no charge • The skeleton equation is the same as the balanced equation Al(s) + CuBr2(aq) Cu (s) + AlBr2 (aq)

  10. Replacing Non-metals with Non-metals • The ion of a non-metal (Cl-) is negatively charged so it can only be replaced with another non-metal F2(g) + 2NaI(s) I2(s) + 2NaF(s)

  11. Double Displacement Reactions • DoubleDisplacement reaction: A chemical reaction in which the positive ions of two compounds change places and form two new compounds • Double Displacement reactions often result in the product of an insoluble solid or precipitate AB + CD AD + CB (A & C are cations and B and D are anions) + +

  12. Double Displacement Reactions • Example: when a yellow aqueous solution of potassium chromate is added to a colorless aqueous solution of silver nitrate a red precipitate of silver chromate is formed: 2AgNO3(aq) + K2CrO4(aq) Ag2CrO4(s) + 2KNO3(aq)

  13. Double Displacement Reactions • Complete and balance the following double displacement reaction. You do not need to predict the states of the products NaCl(aq) + AgNO3(aq)

  14. Double Displacement Reactions Solution: NaCl(aq) + AgNO3(aq) • This is a double displacement reaction so the two cations must switch • Sodium and silver will therefore switch – both have a 1+ charge so the ratio to anions does not change • The skeleton equation is the same as the balanced equation for this reaction NaCl(aq) + AgNO3(aq) AgCl + NaNO3

  15. Summary of Chemical Reactions

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