Chemical Laboratory :Name/Predict/Chemical Compounds & Prepare/Dilute Chemical Solutions.

Define a compound.

A pure substance made of 2 or more types of atoms chemically bonded and cannot be broken down my physical means (e.g., CO₂).

Classify air as an element, compound, or mixture.

Homogeneous mixture.

What is Avogadro’s number?

6.022×10²³ particles/mol (atoms, molecules, or ions).

How many Cl⁻ ions are in 2 moles of MgCl₂?

2.41×10²⁴ Cl⁻ ions (2 mol × 2 × Avogadro’s number).

Calculate the moles in 8.0 g of PCl₃ (molar mass = 137.32 g/mol).

0.0583 mol (mass/molar mass).

What is the mass of 2 mol of ethene (C₂H₄)?

56.12 g (2 × 28.06 g/mol).

Define molarity.

Moles of solute per liter of solution (unit: M or mol/L).

How to prepare 200 mL of 5% (w/v) KI solution?

Dissolve 10 g KI in water to make 200 mL solution.

What is the dilution formula?

MiVi = MfVf (moles before = moles after dilution).

Dilute 25 mL of 12.0 M HCl to 500 mL. Final concentration?

0.6 M (using MiVi = MfVf).

What is an electrolyte?

A substance that dissociates into ions in water (e.g., NaCl).

Is acetic acid a strong or weak electrolyte?

Weak electrolyte (partial dissociation).

Name a non-electrolyte.

Glucose (does not form ions in water).

Is AgCl soluble in water?

No (insoluble, except with Group 1 cations or NH₄⁺).

Assign oxidation numbers to Cr in Cr₂O₇²⁻.

+6 (each Cr; total charge = 2−).

What is oxidation?

Loss of electrons, increase in oxidation number.

Identify the oxidizing agent in: 2Mg + O₂ → 2MgO.

O₂ (gains electrons, reduced).

Is rusting of iron a redox reaction?

Yes (Fe oxidizes to Fe³⁺, O₂ reduces to O²⁻).

Balance: Fe + O₂ → Fe₂O₃

4Fe + 3O₂ → 2Fe₂O₃.

What is a precipitation reaction?

Formation of an insoluble solid (e.g., PbI₂ from Pb(NO₃)₂ + KI).

Write the net ionic equation for: Pb²⁺ + 2I⁻ → PbI₂(s)

(Already given; spectator ions removed).

Does mixing Na₂CO₃ and CuCl₂ cause precipitation?

Yes (forms CuCO₃ solid).

Define spectator ions.

Ions unchanged in a reaction (e.g., Na⁺ in NaCl + AgNO₃).

What is an acid-base neutralization reaction?

Acid + base → salt + water (e.g., HCl + NaOH → NaCl + H₂O).

Name a strong acid and a weak base.

Strong acid: HCl; weak base: NH₃.

Write the reaction for ZnCO₃ + HNO₃.

ZnCO₃ + 2HNO₃ → Zn(NO₃)₂ + H₂O + CO₂.

What gas forms when NH₄Cl reacts with NaOH?

NH₃ (ammonia).

What is the atomic number?

Number of protons in an atom (e.g., Na = 11).

Calculate the mass number of an atom with 6 protons and 6 neutrons.

12 (protons + neutrons).

Define isotope.

Atoms of the same element with different neutrons (e.g., ¹H, ²H).

What is the average atomic mass of carbon (99% ¹²C, 1% ¹³C)?

12.01 amu (weighted average).

How many electrons are in a neutral atom of sodium (Na)?

11 (same as protons).

Where are protons located in an atom?

Nucleus.

What is the charge of an electron?

−1.602×10⁻¹⁹ C (relative charge: −1).

Name the three subatomic particles.

Proton, neutron, electron.

What is a metalloid?

Elements with properties of metals and non-metals (e.g., Si).

Which group contains noble gases?

Group 18 (e.g., He, Ne).

Why are alkali metals reactive?

They have 1 valence electron, easily lost.

What is the electron configuration of oxygen (Z=8)?

2,6 (or 1s² 2s² 2p⁴).

Balance: C₂H₆ + O₂ → CO₂ + H₂O

2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O.

What is a redox reaction in respiration?

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O.

Identify the reducing agent in: Cu + 2Ag⁺ → Cu²⁺ + 2Ag.

Cu (loses electrons).

What is the net ionic equation for Ba²⁺ + SO₄²⁻ → BaSO₄(s)?

(Already simplified; no spectators).

Write the molecular equation for HNO₃ + Ca(OH)₂.

2HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + 2H₂O.

What is a strong electrolyte?

Fully dissociates in water (e.g., NaCl, HCl).

Is Ba(OH)₂ soluble?

Yes (Group 2 hydroxide exception).

What is the oxidation number of O in H₂O₂?

−1 (peroxide exception).

How to prepare CuCO₃ via precipitation?

Mix Cu²⁺ (e.g., CuCl₂) + CO₃²⁻ (e.g., Na₂CO₃).

What is the molar mass of NaOH?

40.00 g/mol (22.99 + 16.00 + 1.01).