Atoms and Mole
Define 1 mole in terms of Avogadro’s number.
1 mole = 6.022×10²³ particles.
What is neutralization?
Reaction between acid and base to form salt + water.
Balance: CH₄ + O₂ → CO₂ + H₂O.
CH₄ + 2O₂ → CO₂ + 2H₂O.
Most reactive alkali metal?
Francium (but practically Cesium).
Why add lime (CaO) to soil?
Neutralizes acidic soil.
How many moles are in 36 g of H₂O?
36 g ÷ 18 g/mol = 2 mol.
Write balanced equation for HCl + NaOH.
HCl + NaOH → NaCl + H₂O.
What is the limiting reagent?
Reagent that is fully consumed first in a reaction.
Why does fluorine have highest electronegativity?
Smallest size, high nuclear charge → strong attraction.
Which ion in acid rain causes corrosion?
H⁺ (from H₂SO₄, HNO₃).
Convert 0.5 mol NaCl into number of formula units.
0.5 × 6.022×10²³ = 3.01×10²³ formula units.
25.0 mL of 0.100 M HCl neutralizes how many moles NaOH?
0.025 × 0.100 = 0.00250 mol NaOH.
10 g H₂ reacts with 80 g O₂. Mass of H₂O formed?
10 g H₂ = 5 mol; 80 g O₂ = 2.5 mol. Limiting O₂ → 5 mol H₂O = 90 g.
Draw Lewis structure for CO₂.
O=C=O (linear).
How does an antacid tablet work?
Neutralizes stomach HCl.
44.8 L of CO₂ at Standard Temperature and Pressure equals how many moles?
44.8 L ÷ 22.4 L/mol = 2 mol.
40.0 mL of 0.200 M H₂SO₄ neutralizes 60.0 mL NaOH. Find NaOH molarity.
Moles H₂SO₄ = 0.040×0.200 = 0.008. Needs 0.016 mol NaOH. 0.060 L used → 0.016/0.060 = 0.267 M.
A reaction is predicted to produce 25 g of NaCl (theoretical yield), but in the lab, only 20 g is obtained (actual yield).
What is the percent yield of the reaction?
Percent Yield=Theoretical Yield/Actual Yield×100 =20/25×100=80%
Difference between ionic & covalent bonding.
Ionic: electron transfer. Covalent: electron sharing.
Why is water a universal solvent?
Polar → dissolves many solutes.
A compound contains 40% C, 6.7% H, 53.3% O. Find empirical formula.
CH₂O.
Diprotic acid requires 30 mL 0.200 M NaOH for 25 mL solution. Find acid molarity.
Moles NaOH = 0.030×0.200 = 0.006. Diprotic → 0.003 mol acid. M = 0.003/0.025 = 0.120 M.
N₂ + 3H₂ → 2NH₃. Liters of H₂ for 22.4 L NH₃ at STP?
22.4 L NH₃ = 1 mol. Needs 1.5 mol H₂ → 33.6 L.
Predict shape of NH₃ using VSEPR (Valence Shell Electron Pair Repulsion theory).
Trigonal pyramidal.
How is molarity used in pharmaceuticals?
Calculating drug solution concentrations.