Flashcards in Lecture 3 Deck (21)
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1
Why is water a good solvent?
Can dissolve many compounds by separating them into their individual ions
2
What are acids?
Substance that release hydrogen ion (H+) as the only cations, when dissolved in water/aqueous solution
Hydrogen ion (H+) makes the solution acidic
When using acid and water, acid is slowly added to water
3
What are bases?
Substances that produce hydroxide ions (OH-) when dissolved in water
OH- makes the solution basic
Base accepts a proton (H+) from H2O creating OH-
4
Strong acids and bases
Acids and bases are classified as either strong or weak
Strong acids and bases react/dissociate completely in water
Yield many H+ / OH- in solution
Weak acids and bases only a fraction of the molecule reacts - (partial dissociation)
Yield few H+ / OH- in solution
5
Acid / Base Neutralization
The reaction of an acid with a base
When added together = neutralization
H+ can react with OH- to form H2O (and a salt)
6
What are salts
Salts are ionic compounds composed of cations and anions with an electrically neutral product
An acid and a base react to form a salt
Compounds that yield ions other than H+ or OH-
NaCl (table salt) contains Na+ (cation) and Cl- (anion)
NaCl > Na+ + Cl-
7
What are electrolytes
Solution that carries (conducts) electricity
Acids, bases, and salts form electrolytes because they produce ions when dissolved in H2O
Ions act as moving electrical charges and carry electricity
In the body they help to maintain functioning of cells and organs in the body
Example:
HCl -> H+ + Cl-
KOH -> K+ + OH-
Cations – positive ion
Anions – negative ion
8
What is an electode?
An electrode is an electric conductor / cell that is referred to as either an anode or a cathode
Anode is (usually) positive
Cathode is (usually) negative
Cations are attracted to the cathode
Anions are attracted to the anode
9
Name some important biological ions?
K+ main intracellular cation (controls electrical impulses of the heart)
Na+ main extracellular cation (edema). Regulate water content
I- used to produce thyroid hormones which regulate metabolism
Ca2+ nerve and muscle function
Mg + sleep, muscle spasm, nerve
HCO3- acid -base balance
10
What are the important blood electrolytes
Important in maintaining the proper functioning of cells and organs
Na+, K+, Cl-, HCO3-
11
What are non electrolytes?
They are sugars
Do not produce ions
Dissolve as molecules
Do not conduct electricity
12
What is pH
pH is a measure of the acidity or alkalinity/basicity of a solution
A measurement of hydrogen ions in solution
(Mathematically) pH is the negative logarithm of the activity of hydrogen ions concentration
13
Name pH range?
A pH decrease of 1 indicates that the solution is 10 times more acidic.
A pH of 2 is 100 times more acidic than a pH of 4
1 — 2 strong acid
2 — 5 moderately strong acid
5 — 7 weak acid
7 neutral
7 — 9 weak base
9 — 12 moderately strong base
12 — 14 strong base
14
pH for body fluids
gastric juices 1.0 – 2.0 (strong acid)
blood 7.35 - 7.45 (weak base)
bile 7.8 - 8.6 (weak base)
urine 4.5 – 8.0 (weak acid)
15
What is a pH meter?
Consists of :
a pH measuring electrode and a reference electrode
measuring electrode is a hydrogen ion sensitive glass bulb reference electrode output does not vary with the activity of the hydrogen ion
It is temperature sensitive.There are two electrodes inside the probe that measure voltage
One is contained in liquid with a fixed pH
The other measures the pH of the sample
A voltmeter in the probe measure the difference between the voltages of the two electrodes
The meter then translates the voltage difference into pH and displays it on the screen
Before taking a pH measurement the meter must be calibrated using a solution of known pH
16
What is a buffer solution?
A solution that will maintain a constant pH when a small amount of acid or base is added to it
It is composed of a mixture of a weak acid or base and a salt of the acid or base
When acid is added, a buffer will absorb H + using the salt portion. Negative ion will bind most of added H+ and pH will not decrease.When a base is added, a buffer will release H+ from the acid portion; this will neutralize the OH-
H2CO3---> H+ HCO3- acid will dissociate releasing H
H+ OH- --> H2O H+ will absorb OH- and pH will not increase
17
What are some biologically important buffers?
Bicarbonate buffer
Maintain a relatively constant blood plasma pH and counteract any force that would alter it
Phosphate buffer
Operates in the internal fluid of all cells
Blood
Buffer pH 7.4 (carbonic acid H2CO3) and bicarbonate ions (HCO3)
18
What is an analytical balance ?
Provide very accurate mass measurements
Close the balance door, while weighing an object, in order to prevent air currents from disturbing the reading
measure to 0.0001 g
Balance has internal calibration weights
Has leveling device
19
What is a top loading balance?
weigh heavier masses than analytical balances
resolution from 1 to 0.001 g
Less sensitive and accurate the analytic balance
20
To ensure readings are correct
Do not spill chemicals on the pan or surrounding area
Clean up any spillage
Switch off the balance between routine use
Position on a vibration-free bench
Position away from draughts
21
