Atoms & Periodic Table
This subatomic particle determines the identity of an element and is found in the nucleus.
Proton (atomic number)
Name the type of bond formed between Na and Cl.
Ionic bond
Identify the type of reaction: 2H₂ + O₂ → 2H₂O
Synthesis (combination) reaction
State Boyle's Law in words.
At constant temperature, pressure and volume of a gas are inversely proportional (P₁V₁ = P₂V₂)
What does a pH of 7 indicate about a solution?
The solution is neutral (neither acidic nor basic)
An atom of carbon-14 has 6 protons. How many neutrons does it have?
8 neutrons (14 - 6 = 8)
Draw the Lewis structure for water and identify its molecular geometry.
Bent/V-shape; two bonding pairs and two lone pairs on O
Balance this equation: __Fe + __O₂ → __Fe₂O₃
4Fe + 3O₂ → 2Fe₂O₃
A gas occupies 4.0 L at 300 K. What volume does it occupy at 600 K (constant pressure)?
8.0 L (Charles's Law: V₁/T₁ = V₂/T₂)
What is the pOH of a solution with [OH⁻] = 1×10⁻⁴ M?
pOH = 4
Moving left to right across a period, this atomic radius trend occurs and why.
Atomic radius decreases -- more protons pull electrons closer
Name the compound N₂O₅
Dinitrogen pentoxide
How many moles are in 44 grams of CO₂? (Molar mass of CO₂ = 44 g/mol)
1 mole
Define molarity and give its units.
Molarity = moles of solute ÷ liters of solution; units = mol/L (M)
In the reaction NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, identify the Bronsted-Lowry acid and its conjugate base.
H₂O is the Bronsted-Lowry acid (proton donor); OH⁻ is its conjugate base. (Bonus: NH₃ is the base and NH₄⁺ is its conjugate acid.)
Element X has 36 protons. Using only the periodic table, predict whether it is more likely to form an ionic bond with Na or with Cl, and explain why.
It is a noble gas (Krypton) — it does not typically form bonds due to its full valence shell. It has 8 valence electrons and is chemically stable/inert. :p
Write the correct formula for iron(III) sulfate.
Fe₂(SO₄)₃
A piece of magnesium ribbon is dropped into hydrochloric acid. Write the balanced equation if this reaction is a single replacement reaction.
Mg + 2HCl → MgCl₂ + H₂
A gas at 1.5 atm and 27°C is heated to 127°C in a rigid container. What is the new pressure?"
Convert to Kelvin: 300 K and 400 K; Gay-Lussac's: P₂ = (1.5 × 400) ÷ 300 = 2.0 atm
Define an endothermic reaction and describe what happens to the surroundings' temperature.
Endothermic: system absorbs energy from surroundings; surroundings feel cooler
Explain why ionization energy generally increases across a period but decreases down a group.
Across a period: more protons, stronger nuclear attraction. Down a group: more shielding and greater distance from nucleus.
Explain why CO₂ is a nonpolar molecule despite having polar bonds.
The two polar C=O bonds are equal and opposite (linear geometry), so dipoles cancel — net dipole = 0
Define limiting reagent and explain how to identify it in a reaction with given masses of two reactants.
The limiting reagent is the reactant that is completely consumed first, limiting the amount of product. Convert both reactants to moles, divide by stoichiometric coefficients — the smaller value indicates the limiting reagent.
Using the ideal gas law, calculate the pressure of 0.5 mol of gas in a 10 L container at 300 K. (R = 0.0821 L·atm/mol·K)
P = nRT/V = (0.5)(0.0821)(300)/10 = 1.23 atm
A weak acid differs from a strong acid in what fundamental way? Give one example of each.
A strong acid fully ionizes in water (e.g. HCl); a weak acid only partially ionizes (e.g. CH₃COOH / acetic acid)