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Determining the physical and chemical properties of pure sodium hydroxide is a challenging task due to its high affinity for water.
In most cases, the properties of impure sodium hydroxide are extrapolated to estimate the properties of the pure substance.
Similarly, when studying aqueous solutions of sodium hydroxide, concentration-dependent physical properties are difficult to determine due to their tendency towards supersaturation.
Some physical properties of solid sodium hydroxide are as follows:
molar mass of sodium hydroxide is 40 g/mol
Appearance: white, crystalline
Density of sodium hydroxide (liquid, 350 °C)= 1.77 g/cm3
mp (soda and water free) 322 ± 2 °C
Sodium hydroxide is a strong base.
Pure sodium hydroxide is strongly hygroscopic, making it difficult to determine its physical and chemical properties. It dissolves in water with the release of heat and forms six distinct hydrates.
During transportation and storage of sodium hydroxide solutions, containers must be heated or insulated as the melting points of some hydrates are above 0°C.
NaOH reacts readily with atmospheric carbon dioxide in the presence of moisture to produce sodium carbonate. Similarly, it reacts with carbon monoxide under pressure and in the presence of moisture to produce sodium formate.
Anhydrous sodium hydroxide reacts slowly with most substances, including metals such as Fe, Mg, Ca, and Cd, which are attacked only slightly at room temperature. However, corrosion rates increase significantly with increasing temperature.
Noble metals like nickel, silver, gold, and platinum are only slightly affected, especially when exposed to oxidizing atmospheres.
In contrast, amphoteric metals such as zinc, aluminum, tin, and lead are attacked by dilute sodium hydroxide solution at room temperature, while iron, stainless steel, and nickel are relatively resistant.
Pressure washing may be a nasty job—and it can be deadly if not performed properly. It is critical to provide sufficient time for preparation.
Here are some safety guidelines for beginners and professionals alike.
When it is pressure-cleaned, old paint might peel off. Prior to 1978, paints may contain lead. Lead paint chips and dust are toxic if breathed or swallowed.
Priority should be given to keeping yourself, your family, and your pets safe.
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Numerous salt solutions undergo precipitation when treated with an aqueous solution of sodium hydroxide.
Upon the addition of a sodium hydroxide solution, a chemical reaction follows, resulting in the formation of a noticeable light green precipitate. The resulting precipitate is comprised of cupric hydroxide, a compound consisting of copper and hydroxide ions. After a series of changes in temperature, the green precipitate we just talked about breaks down into a dark brown precipitate made of cupric oxide.
CuSO4 + 2 NaOH → Cu(OH)2↓ + Na2SO4
Green
Cu(OH)2 [when heated Δ] → CuO↓ + H2O
Black
The aqueous solution of sodium hydroxide engages in a chemical reaction with solutions containing ferrous and ferric salts, leading to the creation of a visually cloudy green precipitate comprised of ferrous hydroxide, as well as a reddish-brown precipitate comprised of ferric hydroxide, respectively.
Dirty Green
Brown
The reaction between a solution of sodium hydroxide and a solution of chromic salt results in the formation of a green precipitate composed of chromic hydroxide.
Green
When the green precipitate is subjected to an excess of sodium hydroxide in the presence of peroxide, it results in the formation of a yellow-colored solution of sodium chromate.
Green ppt Yellow solution