Unit 2 test Flashcards
What is a synthesis Reactions
Simple substances combine to form more complex compounds
Product can either be ionic or molecular
X + Y = XY
Element + element = compound
Compound + element = complex compound
Compound + Compound = very complex compound
Ex. 2Na + Cl2 —> 2NaCl
Specific examples with synthesis reactions
COMBUSTION – means burning with oxygen
METAL + OXYGEN —> METAL OXIDE:
2Mg + O2 (g) —> 2MgO
Note: Metal oxide in water —> BASE
MgO + H2O 🡪 Mg (OH)2
NON-METAL + OXYGEN —> NON- METAL OXIDE:
2S + 3O2 —> 2SO3
Note: non-metal oxide + water —> ACID:
SO3 + H2O —> H2SO4 (aq)
What is a Decomposition reaction
A compound is broken down into simpler substances
XY —> X + Y
Can be broken in to elements or compounds
Often requires energy. i.e. Heat
e.g. 2HCl —> H2(g) + Cl2 (g)
Specific examples with Decomposition
Metal CARBONATES decompose to produce the metal oxide and carbon dioxide gas.
Example: MgCO3 (aq) —> MgO(s) + CO2 (g)
And Carbonic acid decomposing to produce water and carbon dioxide:
H2CO3(aq) → H2O(l) + CO2(g)
What is a Single Displacement Reaction
An element reacts with a compound and displaces a second element from the compound to form an element and a new compound
General form: A + BC —> AC + B
*Don’t forget to follow the activity series. Some reactions will not occur.
If A is more reactive than B (i.e. A»B), the reaction will proceed.
What is a Double Displacement Reaction
AB + CD —> AD + CB
There are usually 2 types of these reactions :
Precipitation reactions - formation of an insoluble compound called a precipitate
eg: AgNO3(aq) + NaCl(aq) —> NaNo3(aq) + AgCl(s)
Neutralization reactions – formation of water and a salt
eg: HCl(aq) + NaOH(aq) 🡪 H2O(l) + NaCl(aq)
*Note: The valence of multivalent elements stays the same on both sides of the equation
What is a Combustion – burning a hydrocarbon
A hydrocarbon is a molecular compound containing only carbon, hydrogen and sometimes oxygen.
Complete combustion of a hydrocarbon always produces only 2 products: CO2 and H2O
Example: Write a balanced chemical equation for the combustion of propane (C3H8).
C3H8 + 5O2 —> 3CO2 + 4H2O
Endothermic vs Exothermic reactions
Exothermic reaction - a chemical reaction that gives out heat to the surroundings.
e.g wood burning
Endothermic reaction - a chemical reaction that absorbs heat from the surroundings
e.g boiling an egg
What is a Neutralization Reaction & its Uses
A neutralization reaction is a double displacement reaction that occurs when:
An acid combines with a base
● The general equation for a neutralization reaction is:
● Acid + base → salt (ionic compound) + water
● H(non-metal) + (metal)OH → (metal)(nonmetal) + HOH
Uses:
The neutralisation reaction is used to control the pH of the soil.
Useful in reversing the damage caused by acid rain on lakes/waterways.
Neutralization with a metal or hydrogen carbonate compound
The reactions between an acid and a metal carbonate or a metal hydrogen carbonate are double displacement reactions that produce carbonic acid.
The carbonic acid is unstable. It rapidly decomposes into water and carbon dioxide.
2HCl(aq) + Na₂CO₃(aq) → H₂CO₃(aq) + 2NaCl(aq)
And shortly after
H₂CO₃(aq) → H₂O(l) + CO₂(g)
Can be written as one reaction:
2HCl(aq) + Na₂CO₃(aq) → H₂O(l) + CO₂(g) + 2NaCl(aq)
How does baking soda work
Baking soda and baking powder are both leavening agents. (make dough rise)
The leavening action of baking soda is activated when it is mixed with an acidic ingredient like fruit juice, vinegar, or buttermilk. The chemical equation for the reaction of the citric acid, H3C6H5O7(aq) , in fruit juice with baking soda is
H3C6H5O7(aq) + 3NaHCO3(s) → Na3C6H5O7(aq) + 3H2O(l) + 3CO2(g)
The 3CO2(g) released from the reaction is the reason the dough rises.
Factors for reactivity
Electron configurations (Energy levels)
Atomic size (radius)
Ionization energies
What factors influence solubility
- Ions with large charges (eg. PO43-) tend to be less soluble.
Reason: Increasing the charge increases the force that holds ions together - Smaller ions (ie. those with a smaller radius) tend to be less soluble.
Reason: Small ions bond more closely together and thus the bond between them is stronger.
What is the Total Ionic Equation (TIE)
Solutes “dissociate” into their ions when dissolved in solution. Therefore, the reaction really looks like:
All of the ions, and the precipitate
2Na+(aq) + S2-(aq) + Fe2+(aq) + SO42-(aq) —> 2Na+(aq) + SO42-(aq) + FeS(s)
What is the Net Ionic Equation
Ions which appear on both sides of the equation in effect
cancel each other out. Therefore:
2Na+(aq) + S2-(aq) + Fe2+(aq) + SO42-(aq) —-> 2Na+(aq) + SO42-(aq) + FeS(s)
Would turn into:
S2-(aq) + Fe2+(aq) 🡪 FeS(s)
