CHEM concentrations Flashcards
The amount of solute in a solution
Concentration
one strength which have known amounts of solute and solvent in a given quantity of solution.
e.g. Normal Saline Solution: 0.85% NaCL
Standard Solution
Qualitative Description
solutions of relatively low concentration
Dilute or Weak
- solutions of relatively high concentration
Concentrated or Strong
•Quantitative Description
equivalent weight solute
Liter solution
Normality (N)
•Quantitative Description
moles solute / Kg solvent
Molality* (m’
•Quantitative Description
moles solute / Liter solution
Molarity(M)
•Quantitative Description
moles solute / total moles solution
Mole Fraction(χA)
%concentration
•% (w/w) =
Mass solute/ mass solution x 100
% (w/v) =
mass solute/ volume solution x 100
% (v/v) =
volume solute/ volume solution x 100
denotes the number of moles of a given substance per liter of solution.
-A capital letter M is used to abbreviate the units of mol/L.
(in units of mol/L, molar, or M) or molar concentration
Molarity
Molarity (M) formula
moles solute / liters of solution
mol/kg, molal, or m) denotes the number of moles of solute per kilogram of solvent (not solution).
•The term ______ solution is used as a shorthand for a “one _____ solution”, i.e. a solution which contains one mole of the solute per 1000 grams of the solvent.
Molality
molality formula
m of solution = mol solute/ kg solvent
as a proportion of the total number of moles in a solution.
•are dimensionless quantities.
molar fraction
mole fraction (X) formula
X of solution= mol solute/ mol solution
denoted “mol %”
•equal to 100% times the mole fraction, is sometimes quoted instead of the mole fraction
mol %= mol solute/ mol solution x100
Equivalent weight solute per liter of solution
•The definition of a gram equivalent varies depending on the type of chemical reaction that is discussed - it can refer to acids, bases, redox species, and ions that will precipitate
Normality
is the only concentration unit that is reaction dependent.
Normality
one equivalent (or equivalent weight) of a substance is the amount of that substance which supplies or consumes one mol of reactive species.
normality calculations
normality formula
Normality (N)= Equivalent wt. solute/ liter solution
T or F
For Bronsted acids and bases, normality refers to how many moles of H+ or OH- there are per liter.
true
T or F
Thus, for hydrochloric acid (HCl) and sodium hydroxide (NaOH) the normality is equal to the molarity.
TRUE
t or f
But for substances like sulfuric acid (H2SO4) or barium hydroxide Ba(OH)2, the normality is twice the molarity.
•For a substances like phosphoric acid (H3PO4) and aluminum hydroxide Al(OH)3, normality would be three times the molarity and so forth.
TRUE
denotes the mass of a substance in a mixture as a percentage of the mass of the entire mixture.
% Concentrations
% Concentrations formula
•% (w/w) = mass solute/ mass solution x 100
t or F
Volume-volume percentage (sometimes referred to as percent volume per volume, % v/v) describes the volume of the solute in mL per 100 mL of the resulting solution.
This is most useful when a liquid - liquid solution is being prepared, although it is used for mixtures of gases as well.
TRUE
used especially in to denote relative proportions in measured quantities; particularly in low-value (high-ratio) proportions at the parts-per-million (ppm), parts-per-billion (ppb), and parts-per-trillion (ppt) level.
Parts Per Notation
Since parts-per notations are quantity-per-quantity measures, they are known as dimensionless quantities; that is, they are pure numbers with no associated units of measurement
Parts Per Notation
often used in the measure of dilutions (concentrations) for instance, for measuring the relative abundance of dissolved minerals or pollutants in water.
Parts-per notation
measure of concentration similar to molarity.
Formal Concentration (F)
used when solving chemical equilibrium problems. It is calculated based on the formula weights of chemicals per liter of solution.
Formal Concentration (F)
The difference between ______ and molar concentrations is that the formal concentration indicates moles of the original chemical formula in solution, without regard for the species that actually exist in solution. Molar concentration, on the other hand, is the concentration of species in solution.
Formal
Reducing the concentration of a solution
Dilution
The total number of solutes in the solution remains the same after ________, but the volume of the solution becomes greater, resulting in a lower molarity, ppm, mg/L, or % concentration.
Dilution
(t or f)
When a solution is diluted, solvent is added to lower its concentration.
The amount of solute remains constant before and after the dilution:
moles BEFORE = moles AFTER
TRUE
(t or f)
You dilute a solution whenever you add solvent to a solution. Adding solvent results in a solution of lower concentration. You can calculate the concentration of a solution following a dilution by applying this equation:
•CiVi = CfVf
•where C is the concentration, V is volume, and the subscripts i and f refer to the initial and final values.
true
is a method in chemistry that allows quantitative analysis of the concentration of an unknown acid or base solution.
Titration
It makes use of the neutralization reaction that occurs between acids and bases, and that we know how acids and bases will react if we know their formula.
Titration
equipment used in a titration are:
Burette
•Acid/Base Indicator (the one used varies depending on the reactants)
•Erlenmeyer flask
•Standard Solution (a solution of known concentration, a common one is aqueous Na2CO3)
•Solution of unknown concentration
Titration Formula
CaVa = CbVb
•Ca = concentration of the acid
•Va = volume of the acid
•Cb = concentration of the base
•Vb = volume of the base
There are three types of Titration
1) strong acid and strong base
2) weak acid and strong base
3) strong acid and weak base
