Chemical reactions

Question 1

What is a combustion reaction?

Answer 1

A combustion reaction is a reaction that produces CO2 and H2O that looks like this:
CxHy + O2 = CO2 + H2O
or this:
CxHyOz + O2 = CO2 + H2O
or this:
CxHy(OH)z + O2 = CO2 + H2O

Question 2

What is a synthesis/combination reaction?

Answer 2

In a synthesis/combination reaction, you’re usually taking smaller things and making it into something larger. Almost all two element reactions and synthesis reaction. (A+B –> AB)
Example: Mg + O2 –> MgO

Question 3

What is a decomposition reaction?

Answer 3

In a decomposition reaction, you’re usually breaking down something into smaller things. (AB –> A + B)
Example: MgO3 + Heat –> MgO + CO2

Question 4

What is a single replacement reaction/single displacement reaction?

Answer 4

In a single replacement/single displacement reaction, you’re switching things around (A + BC = AC + B)
Example: Zn + CuCl2 –> ZnCl2 + Cu

Question 5

What is a double replacement/double displacement reaction?

Answer 5

In a double replacement/double displacement reaction, you’re switching things around (AB + CD = AD + BC)
Example: HCl + NaOH -> NaCl + H2O

Question 6

What is a precipitation reaction?

Answer 6

A precipitation reaction is a type of double replacement/double displacement reaction where you’re mixing two aqueous phases and get a solid product.
Example: AgNO3 (aq) + NaCl (aq) –> AgCl (s) + NaNO3 (aq)

Question 6

What is a neutralization reaction?

Answer 6

A neutralization reaction is a type of double replacement/double displacement reaction where you mix a strong acid (aq) with a strong base (aq) and get water and salt
Example: HCl (acid) + NaOH (base) –> NaCl (salt) + H2O (water)

Question 7

What is a gas evolution reaction?

Answer 7

A gas evolution reaction is a type of double replacement/double displacement reaction where you mix two aqueous phases and get a gas.
Example: Na2S (aq) + HCl (aq) –> NaCl (aq) + H2S (g)

Question 8

What time is a double replacement/double displacement reaction NOT considered a reaction?

Answer 8

When you mix aqueous reactants and get only aqueous products.

Question 9

What is a redox reaction?

Answer 9

A redox reaction is a reaction that involves the transfer of electrons.

Question 10

What is the reactivity series of metals?

Answer 10

The reactivity series determines how reactive a metal is. It is used to determine whether or not a single replacement/single displacement reaction will take place.

Question 11

Name the reactivity series from least to most reactive.

Answer 11

Highly Unreactive:
Pt, Au, Ag, Hg, Cu, Bi, Sb
Comparison:
Hydrogen
Reacts with acids:
Pb, Sn, Ni, Co, Cd, Fe, Cr, Zn, Mn, Al, Mg
Reacts with water:
Ca, Sr, Ba, Li, Na, K

Question 12

How can we use the reactivity series of metals to determine if a single replacement/single displacement reaction will occur?

Answer 12

In A + BC –> AC + B
If A is higher than B on the reactivity series (that is, more reactive), then the single replacement reaction will most likely occur.
Example: Fe + 2HCl –> FeCl2 + H2 will occur because Fe is higher than H on the reactivity series.

Question 13

What is the difference between oxidation and reduction?

Answer 13

Oxidation is a loss of electrons. Reduction is a gain of electrons.

Question 14

How do you write the total ionic equation?

Answer 14

First, take everything in their aqueous phase and separate it into their respective elements (Egs,: 2HCl –> 2H^+ + 2Cl^-)
Note: Subscripts are converted to coefficients (Al2 –> 2Al)

Note: Certain substances may be in their aqueous phase, but they may not ionize completely so you shouldn’t separate them (weak acids, weak bases)

Question 15

How do you write net ionic equation?

Answer 15

The net ionic equation is the total ionic equation but the respective ions (that is, ions that are the same on both sides of the equation) are removed. If possible, simplify the coefficients afterwards.
Note: The same elements, even with the same coefficients, if they don’t have the same charge, they are not respective ions.

Question 16

What is the reactivity series of halogens?

Answer 16

The reactivity series of halogens is the order of how reactive each halogen is.

Question 17

Name the reactivity series of halogens (most to least)

Answer 17

Fl2, Cl2, Br2, I2, At, Ts

Question 18

How can we use the reactivity series of halogens to determine if a single displacement reaction will occur?

Answer 18

A + BC = AB + C
If A is more reactive then C, the reaction will occur.
Example: Cl2 + 2NaBr –> Br2 + 2NaCl

Question 19

What is a salt in chemistry?

Answer 19

Something that comes from an acid-base reaction.

Question 20

H + OH always equals:

Answer 20

H2O (Water)

Question 21

Write the chemical equation and net ionic equation for Na2CO3 + HCl

Answer 21

Na2CO3 + HCl –> 2NaCl + H2CO3 –> NaCl + H2O + CO2

Chemical Equation: Na2CO3 (aq) + 2HCl (aq) –> 2NaCl (aq) + H2O (l) + CO2 (g)

Total Ionic Equation:
2Na^+ + CO3^2- + 2H^+ + 2Cl^- –> 2Na^+ + 2Cl^- + H2O + CO2

Net Ionic Equation:
CO3 + 2H –> H2O + CO2