Reactions

Question 1

What does a higher nuclear charge mean in an atom

Answer 1

Higher Zeff pulls electrons closer, decreasing atomic and ionic radii, and increasing ionization energy and electronegativity.

Question 2

Ionization Energy

Answer 2

Ionization energy (IE) is the minimum energy required to remove an electron from a gaseous atom in its ground state. It is easier to remove if it’s further away from the nucleus, thus, easier to remove if the atomic radius is bigger.

Question 3

As ionization energy decreases, reactivity _____ for metals

Answer 3

increases

Question 4

displacement reactions with halogens

Answer 4

To predict halogen displacement reactions, remember that a more reactive halogen will always replace a less reactive halide ion in a compound.

Question 5

H2O + metal in groups 1 or 2

Answer 5

H2O + metal –> hydroxide
example:
Na + H2O –> 2NaOH

Question 6

Non-metal oxides react with water to produce___

Answer 6

Acids

Example
SO2 + H2O –> H2SO3

Question 8

Rules for assigning oxidation states (numbers)

Answer 8

1. The oxidation state of an atom in its elemental form is always 0. This applies to:
   * Single atoms like Na, O₂, or Cl₂.
   * Diatomic molecules like H₂ or N₂.
2. The sum of the oxidation states of all atoms in:
   A neutral compound is 0.
   A polyatomic ion equals the charge of the ion.
3. Fluorine is always −1(it’s the most electronegative element).
4. Group 1 metals (e.g., Na, K) are always +1.
5. Group 2 metals (e.g., Mg, Ca) are always +2.
6. Hydrogen is usually +1, except in metal hydrides (e.g., NaH), where it’s −1.
7. Oxygen is usually −2, except in peroxides (e.g., H₂O₂, where it’s −1) or when bonded to fluorine (e.g., OF₂, where it’s +2).
   !!! Common mistake: Many students assume oxygen is always −2, forgetting exceptions like peroxides or compounds with fluorine.

Question 9

empirical formula to molecular formula

Answer 9

To find the molecular formula from the empirical formula, divide the molar mass of the compound by the molar mass of the empirical formula. Multiply the subscripts in the empirical formula by this factor.

Question 11

How to know if the reaction is endothermic or exothermic?

Answer 11

Breaking bonds requires energy (endothermic), while forming bonds releases energy (exothermic).

Question 12

incomplete combustion products

Answer 12

H2O + CO

Question 13

Heat transfer formula

Answer 13

The heat transferred during a reaction can be calculated using the formula: Q = mcΔT
where:
Q: Heat transferred (in joules, J)
m: Mass of the substance being heated (in grams, g)
c: Specific heat capacity of the substance (in J g⁻¹ K⁻¹) 4.18 for water
ΔT: Temperature change (in kelvin, K, or degrees Celsius, °C) calculated final - initial

Question 14

ΔH equals _____ (NOT using enthalpies of products and reactants)

Answer 14

-(Q/n)
-(Heat/moles)
ΔH = -(Q/n)

Question 15

Kc only changes with

Answer 15

temperature

Question 16

In an equilibrium, changes in pressure only affect __

Answer 16

gases

Question 17

The element being reduced

Answer 17

gains electrons and is the oxidizing agent

Question 18

the element being oxidized

Answer 18

loses electrons and is the reducing agent

Question 19

visible light emitted

Answer 19

from a higher state to n = 2

Question 20

isomers

Answer 20

same formula different arrangement

Question 21

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