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03 Anyagi halmazok

2014.04.09

Masses and States

 

 

  • Mass of the particles

Mass: state depends on

  • Temperature
  • Pressure
  • Volume

States:

  • Gas
  • Liquid
  • Solid
  • Plasma (very high temperature, nuclei and free electrons, e.g. Sun)

Standard state: 0,1 MPa, 298,16oK (25oC)

Gases

Particles move freely in straight direction and constant speed

A lot of space, very small interactions between them

If they meet clash rigidly

No constant shape and volume

Pressure: particles are hitting the wall of the vessel

Diffusion: movement of particles from a high concentration to a lower concentration until they are spread evenly

Avogadro’s Law

Under the same condition of temperature and pressure, equal volumes of all gases contain the same number of molecules

Molar volume of a gas:

25oC (standard state):                   24.5 dm3

20oC (room temperature):          24.0 dm3

0oC (normal state):                         22.41 dm3

Tasks

What is the volume of 4 moles of hydrogen gas?

What is the volume of 7.5 moles of chlorine gas?

How many moles are there in 12 litres of CO2 gas?

How many moles are there in 668 millilitres of HF gas?

More tasks

  • What is the volume of 4 grams of hydrogen gas?
  • What is the volume of 88 grams of NH3 gas at 20oC?
  • How many molecules are there in 145 dm3 of SO2 gas?
  • How many oxygen atoms are there in 33.7 dm3 of CO2 gas at 0oC?
  • We have a mixture of HCl and CO2 gases. Amount of the CO2 is 45%, the whole volume of the mixture is 137.9 l. How many grams of chlorine are there in this mixture at 0oC?
  • Homework

What is the volume of 5 kg of CH4 gas at 25oC?

How many electrons are there in 31 cm3 of HF gas?

The volume of our bottle is 0.75 l. How many grams of H2S gas can be filled in it at 20oC?

Liquids

Particles are closer to each other

Constant volume

Interaction between particles is not enough strong to fix them: no constant shape

Particles roll on each other

Evaporation: particle leaves the liquid and becomes a gas

Diffusion: speed is lower than in gases

Solutions

Solution (homogenous mixture): solute is dissolved in a solvent

Polar solvent can dissolve polar molecules and ions

Nonpolar solvent can dissolve nonpolar substances

Saturated solution: cannot dissolve more solute

Solubility: g (solute)/100 g solvent in a saturated solution

It depends on temperature: if temperature increases

  • Liquid and solid solute: solubility increases
  • Gas solute: solubility decreases M52.3

Speed up:

  • Grinding of a solid substance: surface area increases
  • Stirring: diffusion increases
  • Dissolution

Exothermic: heat is given out (temperature of the surroundings goes up) ΔHsolution is negative

Endothermic: heat is taken in (temperature of the surroundings goes down) ΔHsolution is positive

ΔHsolution: amount of energy change if 1 mole of a substance is dissolved

Dissolution of ionic compounds

NaCl lattice in water: Cl- ions are attracted to the partially ( + ) H atoms,
 Na+ ions are attracted to the partially ( - ) O atoms.

This pulls the ions from the crystalline solid, where they become surrounded by water molecules (hydrated ions in a hydration shell)

Dissolution of polar molecules

HCl molecule

  • H is partially +, Cl is partially - charged
  • Cl is attracted to the partially ( + ) H atoms,
     H is attracted to the partially ( - ) O atoms
  • This draws the particles apart each other
  • Bonding electron pair is ‘robbed’ by chlorine:
  • H+ and Cl- ions are hydrated

Composition of solutions

Percentage by mass (w/w%) – tömegszázalék (m/m%)

  • wB% = (mB/mS)x100
  • Tömeg% = (m oldott anyag /m oldat )x100

Percentage by volume (w/w%) – tömegszázalék (m/m%)

  • VB% = (VB/VS)x100
  • Térfogat% = (V oldott anyag /V oldat )x100

Tasks

How many g sodium chloride and water does 100 g 5 w/w% sodium chloride solution contain?

5 g sodium chloride is dissolved in 100 g of water. What is the percentage by mass ratio of NaCl?

How many g 36 w/w% solution can be prepared from 60 g potassium chloride?

How many g glucose and water does 325 g 7 w/w% glucose solution contain?

Molarity – anyagmennyiség-koncentráció

  • cB = nB/Vs                            (mol/dm3)
  • Anyagmennyiség-koncentráció = az oldott anyag anyagmennyisége / az oldat térfogata
  • C = n oldott anyag / V oldat                     (mole/dm3)

Mass concentration - tömegkoncentráció

  • ρB = mB/Vs
  • Tömegkoncentráció = az oldott anyag tömege / az oldat térfogata
  • Tasks

What is the molarity of the solution whose 500 cm3 contains 2 g sodium hydroxide?

How many mol and g sodium hydroxide does 200 cm3 0.5 mol/dm3 NaOH solution contain?

How shall we prepare 250 cm3 0.2 mol/dm3 potassium nitrate solution?

What is the molarity and mass concentration of the solution whose 200 cm3 was prepared from 11.7 g sodium chloride?

Density: ρ = m / V (g/cm3)

Mass and volume can be transformed

Tasks:

The density of the 5 mole/dm3 potassium hydroxide solution is 1.216 g/cm3. Calculate the

  • Mass concentration
  • Percentage by mass composition

The density of the 14 w/w% copper(II)sulphate solution is 1.154 g/cm3. Calculate the

  • Mass concentration
  • Molarity of the solution

Solid state

Strong interaction between particles

Particles are shaking in a fixed position

Fixed shape and volume

Melting: particles leave their position at a temperature

  • Types of solid substances

Crystal substances:

  • Particles are ordered in a lattice
  • Melting point
  • E. g. salt, sugar, metals

Amorphous substances

  • No order
  • Increasing temperature: get softer
  • E. g. wax, honey, glass, fat

Colloids

 

Homogenous mixture

Colloidal system

Heterogenous mixture

Size of particles

Less than 1 nm

Between 1 and 500 nm

More than 500 nm

Visibility of particles

No

Only as a mass (or by electron microscope)

Yes

Surface area

No

Exists, huge

Exists

 

  • A special type of mixtures

Properties of colloids

  • Tyndall effect
  • Large surface area: adsorption (e.g. gas mask)

Colloidal solutions:

  • Sol: liquid, dispersed particles are surrounded by hydration shell
  • Gel: jelly, not enough water to form perfect hydration shell

Coagulation: dispersed particles lose their hydration shell and cohere (become a heterogeneous mixture)

 

Heterogenous systems

Medium / 

Dispersed phase

Phases

Gas

Liquid

Solid

Continuous medium

Gas

NONE

Liquid aerosol

Solid aerosol

(All gases are mutually miscible)

Examples:spray fog,

Examples: smoke

Liquid

Foam

Emulsion

Suspension

Example: shaving foam

Examples: milk, mayonnaise

Examples: pigmented ink, blood

Solid

Solid foam

Solid emulsion

Solid suspension

Example: styrofoam

Examples: Butter

Example:

 

 

alloys