Search results
Results From The WOW.Com Content Network
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO 4 ·2H 2 O. [4] It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster , drywall and blackboard or sidewalk chalk .
Phosphogypsum is a by-product from the production of phosphoric acid by treating phosphate ore with sulfuric acid according to the following reaction: Ca 5 (PO 4) 3 X + 5 H 2 SO 4 + 10 H 2 O → 3 H 3 PO 4 + 5 (CaSO 4 · 2 H 2 O) + HX where X may include OH, F, Cl, or Br
where A and B are reactants C is a product a, b, and c are stoichiometric coefficients,. the reaction rate is often found to have the form: = [] [] Here is the reaction rate constant that depends on temperature, and [A] and [B] are the molar concentrations of substances A and B in moles per unit volume of solution, assuming the reaction is taking place throughout the volume of the ...
With judicious heating, gypsum converts to the partially dehydrated mineral called bassanite or plaster of Paris. This material has the formula CaSO 4 ·( n H 2 O), where 0.5 ≤ n ≤ 0.8. [ 8 ] Temperatures between 100 and 150 °C (212–302 °F) are required to drive off the water within its structure.
On the surface of concrete pavements, the ASR can also cause pop-outs, i.e. the expulsion of small cones (up to 3 cm (1 in) in diameter), corresponding to aggregate particle size. A quite similar reaction (alkali-silicate reaction) can occur when clay minerals are present in some impure aggregates, and it may also lead to destructive expansion.
The rate of initial reaction (up to 24 hours) of the cement on addition of water is directly proportional to the specific surface area. Typical values are 320–380 m 2 ·kg −1 for general purpose cements, and 450–650 m 2 ·kg −1 for 'rapid hardening' cements. The cement is conveyed by belt or powder pump to a silo for storage.
The Damköhler numbers (Da) are dimensionless numbers used in chemical engineering to relate the chemical reaction timescale (reaction rate) to the transport phenomena rate occurring in a system. It is named after German chemist Gerhard Damköhler , who worked in chemical engineering, thermodynamics, and fluid dynamics. [ 1 ]
Iron rusting has a low reaction rate. This process is slow. Wood combustion has a high reaction rate. This process is fast. The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. [1]