types of reactions i. synthesis reactions – have only one product. general form: a + x ax ex: 2...
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Types of Reactions
I. Synthesis reactions – have only one product.
General Form: A + X AX
EX: •2 Na(s) + Cl2(g) 2 NaCl(s)•2 H2(g) + O2(g) 2 H2O(l)•CaO(s) + CO2(g) CaCO3(s)
*Metals combine with non-metals in synthesis rxns to form ionic compounds.
EX: Mg + Br2 MgBr2
Synthesis Reactions
Examples:
N2 (g) + 3 H2 (g) 2 NH3 (g)
C3H6 (g) + Br2 (l) C3H6Br2 (l)
2 Mg (s) + O2 (g) 2 MgO (s)
• Two or more substances react to form one product
• Also called“combination rxns”
Practice• Predict the products then write and balance the
following synthesis reaction equations.
• Sodium metal reacts with chlorine gas
• Solid Magnesium reacts with fluorine gas
• Aluminum metal reacts with fluorine gas
Na(s) + Cl2(g)
Mg(s) + F2(g)
Al(s) + F2(g)
II. Decomposition Reactions
• Examples:
CaCO3 (s) CaO (s) + CO2 (g)
2 KClO3 (s) 2 KCl (s) + O2 (g)
2 NaN3 (s) 2 Na (s) + 3 N2 (g)
• Have only one reactant• General Form:
AX A + X• One substance breaks down
into two or more substances
Electrolysis – decomposing a compound by runningan electric current through it.
2 H2O 2 H2 + O2
Special decomposition rxns:
a) Decomposition of metal carbonatesproduces the metal oxide and CO2
EX: MgCO3 MgO + CO2
Write the equation for the decomposition of Na2CO3
Na2CO3 Na2O + CO2
* The decomposition of binary compoundsproduces the two elements in the compound.
EX: 2 NaCl(l) 2 Na(s) + Cl2(g)
N2O4 N2 + 2 O2
b. Decomposition of metal hydroxidesproduce the metal oxide and water.
EX: Mg(OH)2 MgO + H2O
Write the equation for thedecomposition of KOH.
KOH K2O + H2O2
c. Carbonic acid rapidly decomposes upon its formation:
H2CO3(aq) H2O(l) + CO2(g)
Practice• Predict the products then write and balance the following decomposition
rxn equations:• Solid Lead (IV) oxide decomposes
• Aluminum nitride decomposes
• Calcium carbonate is decomposed by heating
• Copper(II) hydroxide is decomposed
PbO2(s)
AlN(s)
CaCO3
Cu(OH)2
III. Single Replacement Reactions
An element replaces another element in a compound.
General forms:
A + BX B + AX (metal takes place of metal)
or
Y + BX X + BY (nonmetal takes place of nonmetal)
These rxns usually occur in solution.
EX: Cu(s)+ 2 AgNO3(aq) 2 Ag(s) + Cu(NO3)2(aq)
Cl2(g) + 2 NaBr2(aq) Br2(l) + 2 NaCl(aq)
*** For a single replacement rxn to occur, an element must be more reactive
than the element it replaces***
See the “Activity Series of Elements” on the back of your periodic table. In order for an elementto replace another element in a compound, it must be higher than that element on the activity series.
Cu(s)+ 2 AgNO3(aq) 2 Ag(s) + Cu(NO3)2(aq)
Occurs - Copper is more reactive than silver
Cl2(g) + 2 NaBr2(aq) Br2(l) + 2 NaCl(aq)
Occurs - Chlorine is more reactive than bromine
Al(s) + NaCl(aq)
Aluminum is LESS reactive than sodium.
No Rxn
Br2(l) + NaCl(aq) No Rxn
Remember that metals replace metals,and nonmetals replace nonmetals.
Bromine is LESS reactive than chlorine
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If the following rxns occur, write the products andbalance the equation; if no reaction occurs, write “No Rxn”
1. Mg(s) + ZnCl2(aq)
2. Al(s) + Pb(NO3)2(aq)
3. Fe(s) + AlCl3(aq)
4. I2(s) + NaCl(aq)
5. F2(g) + LiBr(aq)
Zn(s) + MgCl2(aq)
Pb(s) + Al(NO3)3(aq)2 3 3 2
No Rxn
No Rxn
Br2(l) + LiF(aq)2 2
Write the equation for the rxn of potassium and water.
Special Single Replacement Reactions
a) Group 1 metals and Ca, Sr, and Ba will replace one of the hydrogens in water, producing hydrogen gas and the metal hydroxide.
Ex: Ca + 2 H2O H2 + Ca(OH)2
2 K + 2 H2O H2 + 2 KOH
b) Metals can replace the hydrogen in acids.
Ex: 2 Al(s) + 6 HCl(aq) 3 H2(g) + 2 AlCl3(aq)
Write the equation for the rxn between nitric acidand magnesium metal.
Mg + 2 HNO3 H2 + Mg(NO3)2
*note that hydrogen is listed with the metalson the Activity Series
IV. Double-Replacement Rxns
- the ions of two aqueous compounds“switch places” to form two new compounds.
General Form: AX + BY AY + BX
EX: AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
In order for a double replacement rxn to occur,one of the products must remove its ions from aqueous solution. This can occur when:
1) One of the products is insoluble (forms a solid) in water. A precipitate forms.See the solubility chart on back of periodic table.
Pb(NO3)2(aq) + Na2CrO4(aq) PbCrO4(s) + 2NaNO3(aq)
Check to see if one of the products does not dissolvein water (an “s” on the solubility table). If so, that substance is the precipitate and the rxn occurs. If both products are soluble, no rxn occurs.
Predict the products and balance the equations for the following rxns; if no reaction occurs write “no rxn”
1. AlCl3(aq) + Na3PO4(aq)
2. KNO3(aq) + MgBr2(aq)
AlPO4 + NaCl(s) (aq)3
No Rxn
3. NaCl(aq) + Pb(NO3)2(aq)
4. KNO3(aq) + CaCl2(aq)
5. BaI2(aq) + Na2CO3(aq)
6. CuSO4(aq) + K3PO4(aq)
7. (NH4)2S(aq) + ZnCl2(aq)
2
No Rxn
BaCO3(s) + 2 NaI(aq)
PbCl2(s) + NaNO3(aq)
2. A double replacement rxn occurs if one of the products is water (H2O).
Ex: HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq)
2 HNO3(aq) + Mg(OH)2(s) H2O(l) + 2 Mg(NO3)2(aq)
(these rxns occur when an acid reacts with a base –they’re called neutralization rxns)
Predict the products and balance the following rxn:
H2SO4(aq) + KOH(aq)
3. A double replacement rxn occurs if one of the products is a gas.
Ex: 2 HCl(aq) + Na2CO3(aq) H2CO3(aq) + 2NaCl(aq)
2 HCl(aq) + Na2CO3(aq) H2O(l) +CO2(g) + 2NaCl(aq)
*metal carbonates react with acids to produceH2O, CO2, and a salt.
Predict the products and balance the following rxn:
H2SO4(aq) + CaCO3(aq)