Applied Chemistry
- What does the Gibbs phase rule state and what does F = C − P + 2 mean? In one line The Gibbs phase rule states that for a heterogeneous system in equilibrium, not influenced by gravity, electric or magnetic forc... 1
- Why do we make alloys instead of using pure metals in engineering? In one line Alloys are made to improve properties of a pure metal, such as hardness, strength, corrosion resistance, melting point, castabil... 1
- What is a phase in the phase rule, and how do you count phases in a system? In one line A phase is any homogeneous, physically distinct and mechanically separable part of a system, separated from other parts by a def... 1
- What is a component in the phase rule, and how do you find the number of components? In one line The number of components is the smallest number of independently variable chemical constituents by which the composition of ever... 1
- What are degrees of freedom in the phase rule, and what do invariant and univariant systems mean? In one line Degrees of freedom (F) are the minimum number of independent variables, such as temperature, pressure and concentration, that mu... 1
- What is the reduced (condensed) phase rule and why is it used for alloy systems? In one line For solid–liquid (condensed) systems where the vapour phase is negligible and experiments are done at constant atmospheric press... 1
- How does Pattinson's process use the Pb–Ag phase diagram to desilverise lead? In one line Pattinson's process enriches silver from argentiferous lead (lead with a very small silver content) by cooling the melt so that... 1
- How do you read the lead–silver phase diagram and what happens at its eutectic point? In one line The Pb–Ag system is a two-component simple eutectic system whose temperature–composition diagram shows two freezing-point curves... 1
- How do you solve phase rule numericals to find phases, components and degrees of freedom? In one line Phase rule numericals are solved by carefully counting P and C for the given equilibrium and then applying F = C − P + 2 (or F′... 1
- What are the merits and limitations of the Gibbs phase rule? In one line The phase rule is a simple, general way to classify and predict equilibrium behaviour of heterogeneous systems, but it only appl... 1
- What is corrosion and why is it called the reverse of metal extraction? In one line Corrosion is the gradual destruction or deterioration of a metal by chemical or electrochemical reaction with its environment, s... 1
- How does dry or atmospheric corrosion occur, and what decides whether the oxide film protects the metal? In one line Dry corrosion is direct chemical attack of a metal by dry gases (mainly oxygen) forming a surface film, and the nature of this f... 1
- What is the hydrogen evolution mechanism of wet corrosion in an acidic medium? In one line In an acidic, oxygen-poor environment, the metal dissolves at anodic areas and the released electrons reduce H⁺ ions to hydrogen... 1
- How does iron rust in neutral water by the oxygen absorption mechanism? In one line In a neutral or slightly alkaline medium containing dissolved oxygen, iron is oxidised at anodic areas while oxygen is reduced t... 1
- How do selection of metal and proper design help prevent corrosion in engineering structures? In one line Choosing the right (noble or corrosion-resistant) metal for the environment and designing parts so that moisture, crevices and d... 1
- How do the galvanic series position, metal purity and nature of corrosion product affect corrosion rate? In one line Corrosion is faster when the metal is more active (higher in the galvanic series) or coupled with a very different metal, when i... 1
- How do temperature, pH, concentration and moisture of the medium change the rate of corrosion? In one line Corrosion generally speeds up with higher temperature, lower pH (more acidic), higher concentration of corrosive ions and higher... 1
- Why does a small anode with a large cathode corrode so fast, and how does overvoltage affect corrosion? In one line Corrosion is intense when the anodic area is small compared with the cathodic area, and it is slower when the hydrogen overvolta... 1
- What is cathodic protection, and how do sacrificial anode and impressed current methods work? In one line Cathodic protection prevents corrosion by forcing the whole metal structure to act as the cathode, using either a more active sa... 1
- How do anodic and cathodic corrosion inhibitors slow down corrosion? In one line Corrosion inhibitors are substances added in small amounts to the corrosive medium that reduce the rate of corrosion by blocking... 1
- What is the difference between galvanising and tinning as anodic and cathodic metallic coatings? In one line Galvanising coats iron with a more active metal (zinc), giving an anodic coating that protects even when scratched, while tinnin... 1
- What is a fuel and what are the characteristics of a good fuel? In one line A fuel is a carbon-containing substance that burns in air (oxygen) and releases a large amount of heat that can be used economic... 1
- Why do electronic devices and circuit boards corrode, and how is it prevented? In one line Electronic devices corrode because tiny metal tracks, solder joints and connectors are exposed to moisture, ionic contamination... 1
- What is calorific value, and how are gross and net calorific values different? In one line Calorific value is the total quantity of heat liberated when a unit mass (or unit volume) of a fuel is burnt completely in air o... 1