Sodium Hydroxide (NaOH)
NaOH is highly soluble in water, and readily absorbs moisture and carbon dioxide from the air. Dissolution of solid sodium hydroxide in water is a highly exothermic reaction where a large amount of heat is liberated. The following reaction is under consideration. NaOH (s) + H2O (l) => Na+ + OH- . Place the solid sodium hydroxide into the water in the calorimeter and replace the lid immediately. Stir gently until the solid is completely dissolved and record the highest temperature reached. Data and Observations Distilled Water Volume 2 mL Constant Initial Temperature 2°C NaOH Mass 2. g Final Temperature 8°C Calculations 1. Write out a balanced “equation” for the process you .
Chemical changes are characterized by the formation of new substances and the making and breaking of strong chemical bonds. When caustic soda is dissolved in water, strong ionic bonds between sodium and hydroxide ions are disrupted, are broken, and strong bonds are formed between the sodium ions and the water molecules.
The balance of bonds formed versus bonds broken lies in favour of bond formation in that the dissolution is quite exothermic:.
Now this is what does parallel circuit mean in science undergraduate treatment, not an A level treatment. If you are in high school, canvas your teacher's opinion, and adopt it. When sodium hydroxide dissolves in water is it a chemical or physical change? Chemistry Matter Physical and Chemical Changes. Nov 4, My own feeling is that this is a chemical change Explanation: Chemical changes are characterized by the formation of new substances and the making and breaking of strong chemical bonds.
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When sodium hydroxide (NaOH) dissolves in water, it separates into positively - charged sodium ions (cations) and negatively - charged hydroxide ions (anions). These ions move around in the water, free and independent of each other, though cations tend to be surrounded more closely by anions and vice versa. Sodium hydroxide is quite soluble in water (more than 50% by weight), but if more than this . $\begingroup$ Your second answer is close but think about the state of sodium hydroxide before dissolving in water. $\endgroup$ – Ian Fang Apr 16 '15 at 2 $\begingroup$ Got it! NaOH is a solid! $\endgroup$ – jeterpaul Apr 16 '15 at Add a comment | 2 Answers Active Oldest Votes. 3. Liquid sodium hydroxide is colorless and has no odor. It can react violently with strong acids and with water. Sodium hydroxide is corrosive. NaOH can react with moisture from the .
Lye   Ascarite White caustic. Sodium hydroxide , also known as lye and caustic soda ,   is an inorganic compound with the formula NaOH. Sodium hydroxide is a highly caustic base and alkali that decomposes proteins at ordinary ambient temperatures and may cause severe chemical burns. It is highly soluble in water , and readily absorbs moisture and carbon dioxide from the air.
The commercially available "sodium hydroxide" is often this monohydrate, and published data may refer to it instead of the anhydrous compound. As one of the simplest hydroxides, sodium hydroxide is frequently utilized alongside neutral water and acidic hydrochloric acid to demonstrate the pH scale to chemistry students. Sodium hydroxide is used in many industries: in the manufacture of pulp and paper , textiles , drinking water , soaps and detergents , and as a drain cleaner.
Worldwide production in was approximately 60 million tons, while demand was 51 million tons. It is highly soluble in water, with a lower solubility in polar solvents such as ethanol and methanol.
Similar to the hydration of sulfuric acid, dissolution of solid sodium hydroxide in water is a highly exothermic reaction  where a large amount of heat is liberated, posing a threat to safety through the possibility of splashing. The resulting solution is usually colorless and odorless.
As with other alkaline solutions, it feels slippery with skin contact due to the process of saponification that occurs between NaOH and natural skin oils. The viscosity of aqueous NaOH, as with any liquid chemical, is inversely related to its service temperature, i. The viscosity of sodium hydroxide solutions plays a direct role in its application as well as its storage. Pickering in However, solutions of NaOH can be easily supercooled by many degrees, which allows the formation of hydrates including the metastable ones from solutions with different concentrations.
For example, when a solution of NaOH and water with mole ratio When heated, the solid dihydrate might melt directly into a solution at A hot water solution containing A second stable eutectic composition is The third stable eutectic has When solutions with less than It melts congruously at 7. However, at about 4. The "sodium hydroxide" of commerce is often the monohydrate density 1.
Physical data in technical literature may refer to this form, rather than the anhydrous compound. The hydrogen atoms of the hydroxyls form strong bonds with oxygen atoms within each O layer. Adjacent O layers are held together by hydrogen bonds between water molecules. Sodium hydroxide reacts with protic acids to produce water and the corresponding salts. For example, when sodium hydroxide reacts with hydrochloric acid , sodium chloride is formed:.
In general, such neutralization reactions are represented by one simple net ionic equation:. This type of reaction with a strong acid releases heat, and hence is exothermic. Such acid—base reactions can also be used for titrations. However, sodium hydroxide is not used as a primary standard because it is hygroscopic and absorbs carbon dioxide from air. Sodium hydroxide also reacts with acidic oxides , such as sulfur dioxide.
Such reactions are often used to " scrub " harmful acidic gases like SO 2 and H 2 S produced in the burning of coal and thus prevent their release into the atmosphere. For example,. Glass reacts slowly with aqueous sodium hydroxide solutions at ambient temperatures to form soluble silicates.
Because of this, glass joints and stopcocks exposed to sodium hydroxide have a tendency to "freeze". Flasks and glass-lined chemical reactors are damaged by long exposure to hot sodium hydroxide, which also frosts the glass. Sodium hydroxide does not attack iron at room temperatures, since iron does not have amphoteric properties i. Nevertheless, at high temperatures e. Consider the following reaction between molten sodium hydroxide and finely divided iron filings:. A few transition metals , however, may react vigorously with sodium hydroxide.
The pressurization was due to the hydrogen gas which is produced in the reaction between sodium hydroxide and aluminium:. Unlike sodium hydroxide, which is soluble, the hydroxides of most transition metals are insoluble, and therefore sodium hydroxide can be used to precipitate transition metal hydroxides. The following colours are observed:. Aluminium hydroxide is used as a gelatinous flocculant to filter out particulate matter in water treatment.
Aluminium hydroxide is prepared at the treatment plant from aluminium sulfate by reacting it with sodium hydroxide or bicarbonate. Sodium hydroxide can be used for the base-driven hydrolysis of esters as in saponification , amides and alkyl halides. Touching sodium hydroxide solution with the bare hands, while not recommended, produces a slippery feeling.
This happens because oils on the skin such as sebum are converted to soap. Despite solubility in propylene glycol it is unlikely to replace water in saponification due to propylene glycol primary reaction with fat before reaction between sodium hydroxide and fat. Solid sodium hydroxide is most commonly sold as flakes, prills , and cast blocks.
In , world production was estimated at 60 million dry tonnes of sodium hydroxide, and demand was estimated at 51 million tonnes. North America and Asia each contributed around 14 million tonnes, while Europe produced around 10 million tonnes. In the United States, the major producer of sodium hydroxide is the Dow Chemical Company , which has annual production around 3. All of these companies use the chloralkali process.
Historically, sodium hydroxide was produced by treating sodium carbonate with calcium hydroxide in a metathesis reaction which takes advantage of the fact that sodium hydroxide is soluble, while calcium carbonate is not. This process was called causticizing. This process was superseded by the Solvay process in the late 19th century, which was in turn supplanted by the chloralkali process which we use today.
Sodium hydroxide is also produced by combining pure sodium metal with water. The byproducts are hydrogen gas and heat, often resulting in a flame. This reaction is commonly used for demonstrating the reactivity of alkali metals in academic environments; however, it is not commercially viable, as the isolation of sodium metal is typically performed by reduction or electrolysis of sodium compounds including sodium hydroxide. Sodium hydroxide is a popular strong base used in industry. Sodium hydroxide is used in the manufacture of sodium salts and detergents, pH regulation, and organic synthesis.
In bulk, it is most often handled as an aqueous solution ,  since solutions are cheaper and easier to handle.
Sodium hydroxide is used in many scenarios where it is desirable to increase the alkalinity of a mixture, or to neutralize acids. For example, in the petroleum industry, sodium hydroxide is used as an additive in drilling mud to increase alkalinity in bentonite mud systems, to increase the mud viscosity , and to neutralize any acid gas such as hydrogen sulfide and carbon dioxide which may be encountered in the geological formation as drilling progresses.
Another use is in Salt spray testing where pH needs to be regulated. Sodium hydroxide is used with hydrochloric acid to balance pH. The resultant salt, NaCl, is the corrosive agent used in the standard neutral pH salt spray test. Poor quality crude oil can be treated with sodium hydroxide to remove sulfurous impurities in a process known as caustic washing. As above, sodium hydroxide reacts with weak acids such as hydrogen sulfide and mercaptans to yield non-volatile sodium salts, which can be removed.
The waste which is formed is toxic and difficult to deal with, and the process is banned in many countries because of this. In , Trafigura used the process and then dumped the waste in Ivory Coast.
Sodium hydroxide is also widely used in pulping of wood for making paper or regenerated fibers. Along with sodium sulfide , sodium hydroxide is a key component of the white liquor solution used to separate lignin from cellulose fibers in the kraft process. It also plays a key role in several later stages of the process of bleaching the brown pulp resulting from the pulping process.
In a similar fashion, sodium hydroxide is used to digest tissues, as in a process that was used with farm animals at one time. This process involved placing a carcass into a sealed chamber, then adding a mixture of sodium hydroxide and water which breaks the chemical bonds that keep the flesh intact.
This eventually turns the body into a liquid with coffee-like appearance,   and the only solid that remains are bone hulls, which could be crushed between one's fingertips. Sodium hydroxide is frequently used in the process of decomposing roadkill dumped in landfills by animal disposal contractors. Italian serial killer Leonarda Cianciulli used this chemical to turn dead bodies into soap.
Sodium hydroxide is a dangerous chemical due to its ability to hydrolyze protein. If a dilute solution is spilled on the skin, burns may result if the area is not washed thoroughly and for several minutes with running water. Splashes in the eye can be more serious and can lead to blindness. Strong bases attack aluminium. Sodium hydroxide reacts with aluminium and water to release hydrogen gas. The aluminium takes the oxygen atom from sodium hydroxide, which in turn takes the oxygen atom from the water, and releases the two hydrogen atoms, The reaction thus produces hydrogen gas and sodium aluminate.
In this reaction, sodium hydroxide acts as an agent to make the solution alkaline, which aluminium can dissolve in. Sodium aluminate is an inorganic chemical that is used as an effective source of Aluminium hydroxide for many industrial and technical applications. Formation of sodium tetrahydroxoaluminate III or hydrated sodium aluminate is given by: .
This reaction can be useful in etching , removing anodizing, or converting a polished surface to a satin-like finish, but without further passivation such as anodizing or alodining the surface may become degraded, either under normal use or in severe atmospheric conditions.
Since the alumina is amphoteric , it dissolves in the sodium hydroxide, leaving impurities less soluble at high pH such as iron oxides behind in the form of a highly alkaline red mud. Other amphoteric metals are zinc and lead which dissolve in concentrated sodium hydroxide solutions to give sodium zincate and sodium plumbate respectively.
Sodium hydroxide is traditionally used in soap making cold process soap, saponification. For the manufacture of biodiesel , sodium hydroxide is used as a catalyst for the transesterification of methanol and triglycerides.
This only works with anhydrous sodium hydroxide, because combined with water the fat would turn into soap , which would be tainted with methanol.