Hydroiodic acid (HI) is a strong acid, formed by hydrogen and iodine. It’s used in organic synthesis and as a reducing agent. It’s highly corrosive and requires careful handling.
| IUPAC Name | Hydroiodic Acid |
| Molecular Formula | HI |
| CAS Number | 10034-85-2 |
| Synonyms | Hydriodic Acid, Hydrogen iodide, Iodane |
| InChI | InChI=1S/HI/h1H |
Hydroiodic Acid Properties
Hydroiodic Acid Formula
The chemical formula of hydrogen iodide is HI. It consists of one hydrogen (H) atom bonded to one iodine (I) atom. This simple formula represents the composition of this strong acid.
Hydroiodic Acid Molar Mass
The molar mass of hydrogen iodide (HI) is approximately 127.91 grams per mole (g/mol). This value is calculated by adding the atomic masses of one hydrogen atom and one iodine atom.
Hydroiodic Acid Boiling Point
Hydrogen iodide has a relatively low boiling point of around -35 degrees Celsius (-31 degrees Fahrenheit). At this temperature, the liquid form of HI changes into a gaseous state.
Hydroiodic Acid Melting Point
The melting point of hydrogen iodide is approximately -51 degrees Celsius (-60 degrees Fahrenheit). At this temperature, the solid form of HI transforms into a liquid state.
Hydroiodic Acid Density g/mL
The density of hydrogen iodide is about 2.85 grams per milliliter (g/mL). This density measurement indicates the mass of HI present in one milliliter of the substance.
Hydroiodic Acid Molecular Weight
Hydrogen iodide has a molecular weight of around 127.91 g/mol. This value is the sum of the atomic weights of hydrogen and iodine in the HI molecule.
Hydroiodic Acid Structure
Hydroiodic acid (HI) features a simple structure. It consists of a hydrogen atom bonded to an iodine atom through a single covalent bond. This molecular arrangement gives HI its characteristic properties.
Hydroiodic Acid Solubility
Hydroiodic acid exhibits high solubility in water. When mixed with water, it readily dissolves, forming a colorless solution. The high solubility contributes to its widespread use in various applications, including chemical synthesis.
| Appearance | Colorless liquid |
| Specific Gravity | 2.85 g/mL |
| Color | Colorless |
| Odor | Pungent |
| Molar Mass | 127.91 g/mol |
| Density | 2.85 g/mL |
| Melting Point | -51°C (-60°F) |
| Boiling Point | -35°C (-31°F) |
| Flash Point | Not applicable |
| Water Solubility | Miscible, forming a colorless solution |
| Solubility | Soluble in organic solvents |
| Vapour Pressure | Not available |
| Vapour Density | Not available |
| pKa | -10 |
| pH | Highly acidic (pH < 1) |
Hydroiodic Acid Safety and Hazards
Hydrogen iodide (HI) poses significant safety hazards due to its corrosive nature. It can cause severe skin burns and eye damage on contact. Inhalation of its vapors leads to respiratory irritation. Proper protective equipment, like gloves and goggles, must be used when handling HI. It should be stored in a well-ventilated area, away from incompatible substances. If accidentally ingested or inhaled, seek immediate medical attention. In case of a spill, neutralize with appropriate agents and dispose of as hazardous waste. Following strict safety protocols and handling with caution is crucial to prevent accidents and injuries.
| Hazard Symbols | Corrosive |
| Safety Description | Causes severe skin burns and eye damage. Harmful if inhaled. |
| UN IDs | UN1787 |
| HS Code | 28111990 |
| Hazard Class | 8 (Corrosive substances) |
| Packing Group | II |
| Toxicity | Highly toxic |
Hydroiodic Acid Synthesis Methods
Hydrogen iodide (HI) can be synthesized using various methods. One common approach involves the direct reaction of iodine (I2) with red phosphorus (P). In this method, I2 is mixed with red phosphorus, which acts as a reducing agent. The reaction takes place in the presence of water, yielding HI and phosphoric acid.
Another method involves the reaction of iodine with hydrazine hydrate (N2H4·H2O). This process requires careful handling due to the potentially hazardous nature of hydrazine hydrate. The reaction results in the formation of HI and nitrogen gas.
Alternatively, the reaction of iodine with concentrated sulfuric acid (H2SO4) can also produce HI. In this method, iodine is mixed with concentrated sulfuric acid, leading to the generation of HI gas, which can be collected and condensed into a liquid form.
It’s essential to note that the synthesis of hydrogen iodide should be conducted with proper safety precautions. The chemicals involved may be hazardous, and the reactions might generate toxic gases. Adequate ventilation, protective equipment, and adherence to safety guidelines are crucial during the synthesis process to ensure a safe and successful production of hydrogen iodide.
Hydroiodic Acid Uses
Hydrogen iodide (HI) finds diverse applications across various industries due to its unique properties. Here are some key uses:
- Organic Synthesis: Organic chemistry utilizes HI as an essential reagent to convert alkyl halides to alkanes, a process known as dehalogenation.
- Pharmaceutical Industry: The production of various pharmaceutical compounds, including iodine-containing drugs and iodinated contrast agents for medical imaging, relies on HI.
- Reducing Agent: HI actively functions as a potent reducing agent in chemical reactions, aiding in the reduction of metal ions to their elemental forms.
- Catalysis: HI actively participates as a catalyst in certain chemical reactions, enhancing reaction rates and improving yield in specific transformations.
- Cleaning and Etching: The electronics and semiconductor industries actively employ HI for cleaning and etching processes due to its ability to dissolve metals and metal oxides.
- Analytical Chemistry: Iodometric titrations in analytical chemistry actively employ HI to determine the concentration of certain substances based on their reaction with iodine.
- Metal Surface Treatment: HI actively plays a role in preparing metal surfaces for plating, soldering, and other surface treatment processes.
- Manufacturing of Iodides: Various industries actively utilize HI to produce iodide compounds for diverse applications in fields like photography, medicine, and organic synthesis.
- Laboratory Reagent: Laboratories actively use HI as a useful reagent for numerous chemical reactions and experiments.
Hydrogen iodide’s versatile properties make it a valuable tool in chemical research, industrial processes, and pharmaceutical development, contributing to advancements in multiple sectors and scientific discoveries.
Questions:
Q: Which compound could be added to hydroiodic acid (HI) to neutralize its acidic properties?
A: A base, such as sodium hydroxide (NaOH), can be added to neutralize hydrogen iodide and form water and a salt.
Q: Is hydroiodic acid a strong acid?
A: Yes, hydrogen iodide is a strong acid, meaning it completely ionizes in water, releasing hydrogen ions.
Q: What is the formula for hydroiodic acid?
A: The formula for hydrogen iodide is HI, representing one hydrogen atom bonded to one iodine atom.
Q: Which of the following is the formula for hydroiodic acid?
A: The formula for hydrogen iodide is HI.
Q: How many milliliters of 0.550 M hydroiodic acid are needed to react with 10.00 ml of 0.217 M CsOH?
A: Approximately 17.58 ml of 0.550 M hydrogen iodide is needed to react with 10.00 ml of 0.217 M CsOH.
Q: Is hydroiodic acid illegal?
A: Hydrogen iodide itself is not illegal, but its use and possession may be regulated due to its potential hazards and applications in illegal activities.
Q: What does hydrogen iodide and magnesium sulfide form?
A: Hydrogen iodide and magnesium sulfide react to form hydrogen sulfide (H2S) gas and magnesium iodide (MgI2) salt.
Q: What happens when you mix hydrogen iodide with baking soda?
A: When hydrogen iodide reacts with baking soda (sodium bicarbonate), it produces carbon dioxide gas, water, and sodium iodide.
Q: How does hydrogen iodide act in water?
A: Hydrogen iodide ionizes in water, releasing hydrogen ions (H+) and iodide ions (I-), resulting in a highly acidic solution.
Q: Sodium hydroxide and hydrogen iodide net ionic equation?
A: The net ionic equation for the reaction between sodium hydroxide (NaOH) and hydrogen iodide (HI) is Na+ + OH- + H+ + I- → Na+ + I- + H2O.