Exam Revision Flash Cards for Chem
(19 cards)
What is a buffer solution?
A buffer solution is a solution that resist small changes in ph when small amounts of an acid or base is added.
Buffer Capacity?
Buffer capacity refers to how much acid or alkali can be added to a buffer solution before there is a drastic change in ph value.
The more concentrated reagents used for the buffer the higher the buffer capacity will be.
Applications of Buffer solutions?
Biological systems: The bicarbonate buffering system regulates blood pH ensuring our cells function optimally. Bicarbonate also moon lights as an ocean buffer, keeping marine pH in check.
Brownsted Lowry Acid
Acid that donates protons to other substances
Brownsted lowry base
Base that accepts protons from other substances
pH indicator
A compound that undergoes colour change in a solution specific range of pH values
Indicator Equation:
HIn(aq) + H2O(l) ⇌ H3O+(aq) + In-(aq)
When the pH of a solution containing the indicator becomes more acidic:
The [H3O+] increases.
To counteract the change, the reverse reaction is favoured which results in a reduction in [H3O+].
This increases the production of HIn, which then shows the acid colour.
Indicators:
Phenolphthalein:
pH Range: Approximately 8 to 10.
Color Transition: It goes from colorless to pink within this pH range1.
Application: Phenolphthalein is commonly used in acid-base titrations.
Methyl Red:
pH Range: Identifies pH values between 4.4 and 6.2.
Color Transition: Below pH 4.4, it appears red; above pH 6.2, it turns yellow; and within the range, it appears orange12.
Application: Useful in determining the acidity or alkalinity of solutions.
Bromothymol Blue:
pH Range: Used for pH values between 6 and 7.5.
Color Transition: It shifts from yellow to blue within this range1.
Application: Often employed in educational demonstrations and laboratory experiments.
Universal Indicator:
Composition: A combination of several indicators, including thymol blue, methyl red, bromothymol blue, and phenolphthalein.
pH Range: Spans from acidic (red) to alkaline (violet), with intermediate colors for neutral and other pH levels.
Application: Provides a broader pH range for rough pH estimation
What colour is bromine water Br2(l)
Orange
why must galvanic cells utilise a spontaneous chemical reaction?
Galvanic Cells convert chemical energy into electrical energy.
This required a potential difference between the electrodes to create a current.
Define Polyprotic Acid
A polypro tic acid is a acid that contains more then 1 ionisable hydrogen per species.
Define Acidity constant
Acidity constant is the degree to which an acid ionises.
A greater Ka value indicates a stronger acid.
Define pH
It is the measure of hydrogen ion concentration.
What is an arrhenius Acid:
An arrhenius acid is an acid that produces an H+ in a solution.
An arrhenius base:
A arrhenius base is a base that produces an OH- ion in the solution.
Define a Monoprotic Acid:
A Monoprotic acid is an acid that has only 1 ionisable hydrogen in water/ can only donate 1 proton.
What is a primary Standard?
A primary standard is a highly pure and stable chemical reagent used to prepare standard solutions.
Key Properties of Standard Solutions:
- High Purity the reagent should be exceptionally pure.
-High stability/Low Reactivity: It must remain stable both in air and solution.
-High equivalent Weight: This minimises mass measurement errors.
-Non-Hygroscopic: To prevent mass change due to water absorption.
Non-toxic and inexpensive: Ideally it should be readily available.
