Difference between revisions of "Monopotassium phosphate"

From Sciencemadness Wiki
Jump to: navigation, search
(Created page with "{{Chembox | Name = Monopotassium phosphate | Reference = | IUPACName = Potassium dihydrogen phosphate | PIN = | SystematicName = | OtherNames = Potassium phosphate monobasic<b...")
 
Line 114: Line 114:
 
==Properties==
 
==Properties==
 
===Chemical===
 
===Chemical===
 +
Monopotassium phosphate is commonly used as a [[buffer]] with a pKa of 6.86, and will react with both acids and bases in solution.
 
Reacting MKP with 1 mole of potassium hydroxide will produce dipotassium phosphate, and further adding phosphoric acid will convert it to tripotassium phosphate:
 
Reacting MKP with 1 mole of potassium hydroxide will produce dipotassium phosphate, and further adding phosphoric acid will convert it to tripotassium phosphate:
  
 
: KH<sub>2</sub>PO<sub>4</sub> + KOH → K<sub>2</sub>HPO<sub>4</sub> + H<sub>2</sub>O
 
: KH<sub>2</sub>PO<sub>4</sub> + KOH → K<sub>2</sub>HPO<sub>4</sub> + H<sub>2</sub>O
 
: K<sub>2</sub>HPO<sub>4</sub> + KOH → K<sub>3</sub>PO<sub>4</sub> + H<sub>2</sub>O
 
: K<sub>2</sub>HPO<sub>4</sub> + KOH → K<sub>3</sub>PO<sub>4</sub> + H<sub>2</sub>O
 +
 +
Using potassium carbonate for the same reaction stops at dipotassium phosphate due to the lower pKa of potassium carbonate.
  
 
===Physical===
 
===Physical===
Line 123: Line 126:
  
 
==Availability==
 
==Availability==
−
MKP is sold in some agricultural stores as fertilizer.
+
MKP is sold in some agricultural stores as fertilizer. Hydroponics stores and companies sell it as a water-soluble nutrient.
  
−
It can also be purchased from pet shops.
+
It can also be purchased from some pet stores for use in household aquariums.
  
 
==Preparation==
 
==Preparation==
−
Potassium phosphate monobasic can be made by reacting [[phosphoric acid]] with [[potassium hydroxide]].
+
Potassium dihydrogen phosphate can be made by the partial neutralization of [[phosphoric acid]] with [[potassium hydroxide]] or [[potassium carbonate]]. Excess phosphoric acid is recommended as it will limit the generation of any monohydrogen phosphate species. It can easily be crystallized from solution due to its lower solubility at ambient temperatures.
  
 
==Projects==
 
==Projects==
Line 139: Line 142:
  
 
===Storage===
 
===Storage===
−
MKP doesn't require special storage and can be stored in any container.
+
MKP is highly stable with time and doesn't require any particular storage conditions.  
  
 
===Disposal===
 
===Disposal===
−
MKP can be dumped in the ground or poured down the drain.
+
MKP is nontoxic and safe to dispose of down a drain or in normal household waste.
  
 
==References==
 
==References==

Revision as of 14:30, 27 September 2018

Monopotassium phosphate
Monopotassium phosphate potassium dihydrogen phosphate sample.jpg
MKP from a pet shop.
Names
IUPAC name
Potassium dihydrogen phosphate
Other names
Potassium phosphate monobasic
KDP
Identifiers
Jmol-3D images Image
Properties
KH2PO4
Molar mass 136.086 g/mol
Appearance White crystalline powder
Odor Odorless
Density 2.338 g/cm3
Melting point 252.6 °C (486.7 °F; 525.8 K)
Boiling point 400 °C (752 °F; 673 K) (decomposes)
22.6 g/100 mL (20 °C)
83.5 g/100 mL (90 °C)
Solubility Slightly soluble in ethanol, methanol
Insoluble in benzene, dichloromethane
Acidity (pKa) 6.86
Hazards
Safety data sheet ScienceLab
Flash point Non-flammable
Related compounds
Related compounds
 Dipotassium phosphate
Tripotassium phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Monopotassium phosphate (MKP) or potassium dihydrogen phosphate (KDP) is a soluble phosphoric acid salt of potassium with the chemical formula KH2PO4.

Properties

Chemical

Monopotassium phosphate is commonly used as a buffer with a pKa of 6.86, and will react with both acids and bases in solution. Reacting MKP with 1 mole of potassium hydroxide will produce dipotassium phosphate, and further adding phosphoric acid will convert it to tripotassium phosphate:

KH2PO4 + KOH → K2HPO4 + H2O
K2HPO4 + KOH → K3PO4 + H2O

Using potassium carbonate for the same reaction stops at dipotassium phosphate due to the lower pKa of potassium carbonate.

Physical

Potassium dihydrogen phosphate is a white solid, soluble in water. It decomposes when heated above 400 °C. MPK's density is 2.338 g/cm3 at standard conditions.

Availability

MKP is sold in some agricultural stores as fertilizer. Hydroponics stores and companies sell it as a water-soluble nutrient.

It can also be purchased from some pet stores for use in household aquariums.

Preparation

Potassium dihydrogen phosphate can be made by the partial neutralization of phosphoric acid with potassium hydroxide or potassium carbonate. Excess phosphoric acid is recommended as it will limit the generation of any monohydrogen phosphate species. It can easily be crystallized from solution due to its lower solubility at ambient temperatures.

Projects

Handling

Safety

MPK is safe to handle and poses little toxicity.

Storage

MKP is highly stable with time and doesn't require any particular storage conditions.

Disposal

MKP is nontoxic and safe to dispose of down a drain or in normal household waste.

References

Relevant Sciencemadness threads

Retrieved from "https://www.sciencemadness.org/smwiki/index.php?title=Monopotassium_phosphate&oldid=9645"