Chemistry Full Test Guide For Unit 3

Topics: Phase Changes, Heating curves, Binary Ionic Nomenclature, Energy Calculations

What does a phase diagram show?

Which phase (solid, liquid, gas) is stable at each combination of temperature and pressure.

What are the axes of a phase diagram?

x-axis = temperature, y-axis = pressure.

Where are the solid, liquid, and gas regions?

Solid: high pressure/low temperature. Gas: low pressure/high temperature. Liquid: in between.

What does a line between two regions represent?

Conditions where the two phases coexist in equilibrium.

Name the three equilibrium curves.

Fusion (solid–liquid), vaporization (liquid–gas), sublimation (solid–gas).

What is the triple point?

The single Temp and Pressure at which solid, liquid, and gas all coexist in equilibrium.

What is the critical point?

The end of the liquid–gas line. Above its critical T and P, liquid and gas can no longer be told apart.

What is a supercritical fluid?

A substance above its critical temperature and pressure. It is dense like a liquid but flows and diffuses like a gas.

Can pressure alone liquefy a gas above its critical temperature?

No.

What is the normal melting point?

The temperature at which solid and liquid coexist at 1 atm.

What is the normal boiling point?

The temperature at which liquid and gas coexist at 1 atm (vapor pressure = 1 atm).

Define sublimation and deposition.

Sublimation: solid → gas directly. Deposition: gas → solid directly.

What is the slope of the solid–liquid line for most substances?

Positive (leans right): more pressure raises the melting point.

What is the slope of water's solid–liquid line?

Negative (leans left): more pressure lowers the melting point.

Why is water's solid–liquid line unusual?

Ice is less dense than liquid water (open hydrogen-bonded lattice), so pressure favors the liquid.

Triple point of water?

0.01 °C and 0.006 atm

Critical point of water?

374 °C and 218 atm

Triple point of CO₂?

−56.6 °C and 5.1 atm

Critical point of CO₂

31 °C and 73 atm

Why does dry ice sublime at 1 atm

CO₂'s triple-point pressure (5.1 atm) is above 1 atm, so no liquid exists at 1 atm. It goes solid → gas at −78.5 °C

when does a substance sublime at normal atmospheric pressure?

When its triple-point pressure is greater than 1 atm.

What does a horizontal move on a phase diagram mean?

Constant pressure, changing temperature (like a heating curve).

What does a vertical move mean?

Constant temperature, changing pressure

Why does water boil at a lower temperature at high altitude?

Lower atmospheric pressure, so the vapor pressure reaches it at a lower T (down the vaporization line).

Why does a pressure cooker cook faster?

Higher pressure raises the boiling point, so the water gets hotter than 100 °C.

When does a liquid boil?

When its vapor pressure equals the external pressure.

How do you find the phase at a given T and P?

Locate the point, the region it falls in is the phase, on a line, two phases coexist.

Which line ends at the critical point? Which does not end?

Liquid–gas ends there. The solid–liquid line continues upward, nearly vertical.

Below the triple-point temperature, which phase changes are possible as pressure changes?

Only solid ↔ gas. No liquid can form.

How does freeze-drying use a phase diagram?

Pressure is kept below the triple point so ice sublimes directly to vapor.

What is a binary ionic compound?

A compound of exactly two elements: a metal cation and a nonmetal anion.

Basic naming rule?

Cation (metal name unchanged) first, then the nonmetal with its ending changed to -ide.

Do ionic names use mono-, di-, tri-?

No. Prefixes are for molecular (covalent) compounds

How do you write a formula from the ions?

Choose subscripts so total positive charge = total negative charge (criss-cross, then reduce).

Criss-cross Al³⁺ and O²⁻.

Al₂O₃.

Charges of Group 1A, Group 2A, and aluminum?

+1, +2, and +3.

Which transition metals have a fixed charge?

Ag⁺, Zn²⁺, Cd²⁺ (no Roman numeral needed)

Anion charges for Groups 5, 6, 7?

−3, −2, −1.

Names of F⁻, Cl⁻, Br⁻, I⁻?

Fluoride, chloride, bromide, iodide.

Names of O²⁻, S²⁻, Se²⁻, N³⁻, P³⁻, H⁻?

Oxide, sulfide, selenide, nitride, phosphide, hydride.

When is a Roman numeral required?

For metals that form more than one cation: most transition metals (except Ag, Zn, Cd), plus Sn and Pb.

What does the Roman numeral mean?

The charge of the cation

What is the Stock system format?

Metal name, then the charge in Roman numerals in parentheses, ex: iron(III)

What is the classical naming system?

Latin-based names with -ous (lower charge) or -ic (higher charge)

Fe²⁺ and Fe³⁺: Stock and classical names?

Iron(II)/ferrous and iron(III)/ferric (see what i mean?)

Cu⁺ and Cu²⁺: Stock and classical names?

Copper(I)/cuprous and copper(II)/cupric.

Sn²⁺ and Sn⁴⁺: Stock and classical names?

Tin(II)/stannous and tin(IV)/stannic.

Pb²⁺ and Pb⁴⁺: Stock and classical names?

Lead(II)/plumbous and lead(IV)/plumbic.

Hg₂²⁺ and Hg²⁺: Stock and classical names?

Mercury(I)/mercurous (a two-atom ion) and mercury(II)/mercuric.

Name NaCl.

Sodium chloride.

Name MgO

Magnesium oxide.

Name CaF₂

Calcium fluoride.

Name K₂S.

Potassium sulfide

When naming something, how should you order the elements?

Metals First

Name Li₃N

Lithium nitride.

Name BaBr₂.

Barium bromide

Name Ag₂S

Silver sulfide (no numeral; Ag is always +1)

Name ZnI₂

Zinc iodide (no numeral; Zn is always +2)

Name FeCl₂

Iron(II) chloride (ferrous chloride)

Name FeCl₃

Iron(III) chloride (ferric chloride)

Name CuO

Copper(II) oxide (cupric oxide)

Name Cu₂O

Copper(I) oxide (cuprous oxide)

Name SnCl₄

Tin(IV) chloride (stannic chloride)

Name PbS

Lead(II) sulfide

Name PbO₂

Lead(IV) oxide

Name Fe₂O₃

Iron(III) oxide (ferric oxide)

Name CrCl₃

Chromium(III) chloride

Name MnO₂

Manganese(IV) oxide

Name CoCl₂

Cobalt(II) chloride

Name Cu₃N

Copper(I) nitride

Name SnF₂

Tin(II) fluoride (stannous fluoride)

Name TiO₂

Titanium(IV) oxide

Name Mg₃P₂

Magnesium phosphide

Formula for calcium nitride?

Ca₃N₂

Formula for aluminum sulfide?

Al₂S₃

Formula for potassium oxide?

K₂O

Formula for barium iodide?

BaI₂

Formula for iron(II) sulfide?

FeS

Formula for copper(II) chloride?

CuCl₂

Formula for lead(IV) sulfide?

PbS₂

Formula for gold(III) chloride?

AuCl₃

Formula for manganese(II) oxide?

MnO

Formula for zinc phosphide?

Zn₃P₂

Formula for cuprous chloride?

CuCl (cuprous = Cu⁺)

Formula for stannic oxide?

SnO₂ (stannic = Sn⁴⁺)

What is the charge of Fe in Fe₂O₃?

+3. Three O²⁻ = −6, shared by two Fe, so +3 each.

What is the charge of Cu in Cu₂S?

+1. One S²⁻ = −2, shared by two Cu, so +1 each: copper(I) sulfide.

What is the charge of Sn in SnS₂?

+4 (two S²⁻ = −4): tin(IV) sulfide.

What is wrong with writing iron(III) chloride as Fe₃Cl?

The Roman numeral is the charge. Fe³⁺ and Cl⁻ give FeCl₃

Is NaOH a binary ionic compound?

No. It has three elements and the polyatomic hydroxide ion, even though the name ends in -ide.

Why does NaCl need no Roman numeral?

Sodium (Group 1A) forms only Na⁺

What does a heating curve plot?

Temperature (y) vs. heat added or time (x) at constant pressure and constant heating rate.

What do the sloped segments represent?

Kinetic energy and temperature rise. Use q = mcΔT.

What do the flat segments (plateaus) represent?

A phase change.

Temperature is constant.

Use q = mΔH.

How many segments for ice at −20 °C to steam at 120 °C?

Five: warm ice, melt, warm liquid, boil, warm steam.

At what temperatures are water's two plateaus?

0 °C (melting) and 100 °C (boiling) at 1 atm.

What is present during a plateau?

Two phases coexisting (solid + liquid, or liquid + gas).

Why does temperature stay constant during a phase change?

Energy goes into potential energy (overcoming attractions), not average kinetic energy. Temperature measures average kinetic energy.

Which plateau is longer for water, melting or boiling?

Boiling, because ΔHvap > ΔHfus.

Why is ΔHvap larger than ΔHfus?

Boiling must fully separate the molecules, but melting only loosens them.