Week 7 - Covalent Bonds, Chemical Indicator, pH Flashcards
Valence electrons
Electrons in the outermost shell of an atom
Formed when one atom accepts or donates one or more of its valence electrons to another atom
Combination of ions.
Requires one positive ion (cation) one negative ion (anion).
Ionic bond
Metal (cation) + nonmetal (anion) =
Ionic bond
Ionic bond compounds
Electrolytes
Occurs when two or more nonmetal atoms co e together and share valence electrons to become stable.
Covalent bonds
Do covalent bonds break in water?
No. Covalent bonds are strong
Compounds containing covalent bonds are
Nonelectrolytes
Have lower melting and boiling points than ionic compounds
Covalent molecules
One pair of electron is shared between atoms
Bond can be represented by a single line or dash
Lewis dot structure.
Single covalent bond
Two pairs of electrons (4) bring shared.
Represented by a double line.
Double covalent bond
Sharing 3 pairs of electrons (6).
Triple covalent bond
Depends on the electronegativity of the atoms involved
Polarity
Attraction of an atom for electrons in a covalent bond
Electronegativity
Two atoms with the same electronegativity will share the bonding electron pairs equally
No separation of charges
Nonpolar covalent bond
Two bonded atoms have different electronegativity, the bonding pairs of electrons will be shared unequally
Polar covalent bonds
Any substance that gives a visible sign, usually by a colour change, of presence or absence of a threshold concentration of a chemical, such as an acid or an alkali in a solution is called:
Chemical indicator
Qualities of chemical indicators are:
Must be both sensitive and easily detectable
Doesn’t change the conditions of the sample
This indicator is either a weak acid or a weak base that exhibits a colour change as the concentration of hydrogen (H+)/ or hydroxide (OH-) ions changes in an aqueous solution:
Acid-Base indicator
Use of acid-base indicators
In titration to identify the endpoint of an acid-bade reaction
Gauge pH values
Change colour in response to different pH values
Litmus paper and pH paper are used for quick and relatively imprecise measurements
Strips of paper that have been treated with this :
Acid-Base indicators
A logarithmic measure of the hydrogen ion concentration of an aqueous solution (pH=-log[H+]) is referred to as:
pH
pH below 7 is:
Acidic
pH greater than 7 is:
Basic
Very strong acids may have a
Negative pH
Very strong bases may have a
pH exceeding 14
Change colour over a narrow range of pH values solution
Display different colours between certain pH limits
pH indicator
Normal pH range for blood
Between 7.35 and 7.45
The glomerular filtrate of blood is usually acidified by the kidneys from a pH of approximately ___ to a pH of _ in the urine
7.4 and 6
The pH of urine may range from
4.5 to 8
Done by measuring different buffer solutions with standardized values
Using buffers with pH 4 and 10
pH meter is adjusted based on any deviations from the buffer’s known pH value
Calibration
A minimum of three standards are require for a calibration curve
Best accuracy
Patient samples have different values and biological characteristics
Sample differences
As the ________, water ionize and form more ______.
Temperature rises and hydrogen ions
