# Concentration.

## Presentation on theme: "Concentration."— Presentation transcript:

Concentration

Concentrated versus Dilute
solvent solute Lower concentration Not as many solute (what’s being dissolved) particles Higher concentration More solute (what’s being dissolved) particles

Concentration Concentration – a ratio of the amount of solute dissolved over the total amount of solution. There are several ways to show concentration – we will only focus on one

Quick Mole Review 1 mole = 6.02 × 1023 molecules
The molar mass of a molecule is found by adding up all the atomic masses in the atom ( from the periodic table) Molecular mass in grams = 1 mole of that molecule

How many moles are in 25.5 g NaCl?
Quick Mole Example Example: How many moles are in 25.5 g NaCl?

How many moles are in 25.5 g NaCl?
Quick Mole Example Example: How many moles are in 25.5 g NaCl? Na Cl 1 22.99 g/mole 35.45 g/mole = + 58.44 g/mole 1 mole NaCl molecules = g 25.5 g NaCl 1 mole NaCl = _______ mole NaCl 0.436 58.44 g NaCl

Molarity Molarity (M) is a concentration unit that uses moles of the solute over the total volume of the solution

Molarity Example Example:
If you dissolve 12 g of NaCl to make 150 mL of solution, what is the molarity?

Molarity Example = _______ mole NaCl 1.4 M NaCl
If you dissolve 12 g of NaCl in 150 mL of solution, what is the molarity? Na Cl 1 22.99 g/mole 35.45 g/mole = + 58.44 g/mole 1 mole NaCl molecules = g 12 g NaCl 1 mole NaCl = _______ mole NaCl 0.21 58.44 g NaCl Remember to change mL to L! 150 mL of water = L 1.4 M NaCl

Dissolving substances
Substances are dissolved by a process called HYDRATION or SOLVATION The solvent attracts to the solute New intermolecular forces are formed The solvent “carries off” the solute particles and surrounds the ions – keeping them dissolved!

Dissolving Ionic Compounds
+ - O H - + Ionic compound water Water molecules are polar and they attract to the charges of the ions in an ionic compound. - + - If the ion attraction is weak enough, the water can successfully pull them apart. + - + - + -

Dissolving Ionic Compounds
+ - O H - + Ionic compound water - As more ions are “exposed” to the solvent, they can be carried off as well. + - + - + - + -

Dissolving Ionic Compounds
+ - O H - + Ionic compound water + - These free-floating ions in the solution allow electricity to be conducted - + - + - + -

Electrolytes Electrolytes – substances that produce free floating ions and can conduct a current when dissolved. Ex. NaCl(s)  Na+1(aq) + Cl-1(aq) BaI2  Ca3(PO4)2  K2O 

Dissolving Covalent Compounds
Solvent, water (polar) + - - + Solute, sugar (polar) Water forms intermolecular forces with the polar ends of the solute and “carries” the solute particles away. - + - + - +

Dissolving Covalent Compounds
Solvent, water (polar) + - - + Solute, sugar (polar) - + NOTICE how the polar covalent molecules themselves do not split into charged ions—the solute molecule stays together and just separates from other solute molecules.

Non-electrolytes NON-ELECTROLYTES - Molecules that separate from other molecules but DO NOT create free-floating ions 1 C6H12O6(s)  1 C6H12O6(aq)

Breaking up Electrolytes
Leave polyatomic ions in-tact (including the subscript within the polyatomic ion) All subscripts not on a polyatomic ion become coefficients Be sure to include charges on the dissociated ions! Example: Break up the following ionic compounds into their ions KNO3 Ca(NO3)2 Na2CO3

Breaking up Electrolytes
Leave polyatomic ions in-tact (including the subscript within the polyatomic ion) All subscripts not within a polyatomic ion become coefficients Be sure to include charges on the dissociated ions! Example: Break up the following ionic compounds into their ions KNO3 Ca(NO3)2 Na2CO3  K+1 + NO3-1  Ca NO3-1  2 Na+1 + CO3-2

Let’s Practice #3 Example:
What are the molarities of the ions made in a 0.75 M solution of Ca(NO3)2

Let’s Practice #3 Ca(NO3)2  Ca+2 + 2 NO3-1 Ca+2 = 0.75 M
Example: What are the molarities of the ions made in a 0.75 M solution of Ca(NO3)2 Ca(NO3)2  Ca NO3-1 For every 1 Ca(NO3)2, there will be 1 Ca+2 and 2 NO3-1 ions Ca+2 = 0.75 M NO3-1 = 1.5 M

Types of Electrolytes Strong Electrolytes Weak Electrolytes
Non-Electrolytes Ionic compounds Strong Acids Strong Bases Ionic Compounds Weak Acids Weak Bases Covalent Compounds Fully Ionize in solution Only a few ions are created in water No molecules separate—ions are not formed STRONGLY CONDUCTS CONDUCTS WEAKLY DOESN’T CONDUCT