Sodium bicarbonate

From Sciencemadness Wiki
Jump to: navigation, search
Sodium bicarbonate
Sodium bicarbonate sample.jpg
Food grade sodium bicarbonate
Names
IUPAC name
Sodium hydrogen carbonate
Other names
Baking soda
Bicarb
Bicarbonate of soda
Nahcolite
Thermokalite
Properties
NaHCO3
Molar mass 84.0066 g/mol
Appearance White solid
Odor Odorless
Density 2.20 g/cm3 (solid)
1.1-1.3 g/cm3 (powder)
Melting point 50 °C (122 °F; 323 K) (decomposes to Na2CO3)
Boiling point Decomposes
6.9 g/100 ml (0 °C)
8.2 g/100 ml (10 °C)
9.6 g/100 ml (20 °C)
10 g/100 ml (25 °C)
11.1 g/100 ml (30 °C)
12.7 g/100 ml (40 °C)
14.5 g/100 ml (50 °C)
16.5 g/100 ml (60 °C)
19.5 g/100 ml (80 °C)
23.6 g/100 ml (100 °C)
Solubility Insoluble in ethanol, halocarbons, hydrocarbons
Solubility in acetone 0.02 wt% (22 °C)
Solubility in methanol 2.13 wt% (22 °C)
Acidity (pKa) 10.329
Thermochemistry
102 J·mol-1·K-1
−947.7 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
4,220 mg/kg (rat, oral)
Related compounds
Related compounds
Potassium bicarbonate
Sodium carbonate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium bicarbonate, sodium hydrogen carbonate, bicarbonate of soda, Bicarb, or baking soda, is a commonly used reagent with the chemical formula NaHCO3. Generally appearing as a fine white powder or fine crystals, sodium bicarbonate is an amphoteric compound, fulfilling roles as both an acid and a base in different chemical reactions, though it is more often thought of as a base.

It exists in nature as the rare mineral nahcolite (thermokalite).

Properties

Chemical

Sodium bicarbonate will react with acids to release carbon dioxide.

NaHCO3 + HX → H2O + CO2 + NaX

Sodium bicarbonate reacts with bases such as sodium hydroxide to form carbonates:

NaHCO3 + NaOH → Na2CO3 + H2O

Sodium bicarbonate slowly decomposes to form sodium carbonate above 50 °C, though the rate of decomposition is much higher at or above 200 °C.

Physical

Sodium bicarbonate forms white crystals and is soluble in water. It has a slightly salty taste, similar to that of sodium carbonate.

Acquisition

Relatively pure sodium bicarbonate can be purchased in supermarkets, cheaply and in large quantities, as baking soda. It is essential to buy unscented baking soda, as scented baking soda may form side products with other reactants or give a nauseating odor in many reactions.

Preparation

Sodium bicarbonate can be prepared by bubbling carbon dioxide in a concentrated solution of sodium carbonate. Cool the solution until sodium bicarbonate precipitates, then filter and air dry the bicarbonate precipitate. Do not boil the bicarbonate solution, as sodium bicarbonate decomposes above 50 °C.

Uses

Sodium bicarbonate is one of the most versatile and commonly encountered compounds in amateur chemistry. Neutralization of sodium bicarbonate with acids yields a sodium salt and large amounts of carbon dioxide; reaction vessels should have ample headroom to prevent spills. Due to its ease of access and relative cheapness, sodium bicarbonate can be used to neutralize and clean acid spills as well; it is convenient, because the reaction of neutralization in its case is endothermic and results in cooling, unlike with hydroxides, which give very exothermic reactions that may lead to boiling and sprinkling of acids. As many carbonates are not water-soluble, sodium bicarbonate can be used in double replacement reactions to produce the carbonates of many metals.

Sodium bicarbonate, like sodium carbonate, can be used in acid-base titrations.

Handling

Safety

Sodium bicarbonate is non-toxic, but if swallowed it will neutralize the gastric acid and release carbon dioxide, causing burps or if too much is ingested, vomit. It will also increase the sodium level in blood if large quantities are consumed.

Storage

Sodium bicarbonate should be stored in closed bottles away from any acidic vapors.

Disposal

Sodium bicarbonate can be poured down the drain or dumped in trash.

References

Relevant Sciencemadness threads