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Water-reactive substances
Water-reactive substances are those that spontaneously undergo a chemical reaction with water, often noted as generating flammable gas. Some are highly reducing in nature. Notable examples include alkali metals, lithium through caesium, and alkaline earth metals, magnesium through barium.
Some water-reactive substances are also pyrophoric, like organometallics and sulfuric acid. The use of acid-resistant gloves and face shield is recommended for safe handling; fume hoods are another effective control of such substances.
The UN Recommendations on the Transport of Dangerous Goods Model Regulation classifies Water-reactive substances as Class 4.3 (substances which in contact with water emit flammable gases). Countries worldwide have adopted the UN model regulations into their transport of dangerous goods regulations for both international and domestic transportation by road, rail, air and sea. In an NFPA 704 fire diamond's white square, and in similar contexts, they are denoted as "W". The classification of substances as water-reactive is largely a consideration for the safety of firefighting and transportation operations.
All chemicals that react vigorously with water or liberate toxic gas when in contact with water are recognized for their hazardous nature in the "Approved Supply List", or the list of substances covered by the international legislation on major hazards many of which are commonly used in manufacturing processes.
The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table - they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.
The Group 1 metal (M) is oxidised to its metal ions, and water is reduced to hydrogen gas (H2) and hydroxide ion (OH−), giving a general equation of:
The Group 1 metals or alkali metals become more reactive as their number of energy levels increases.
The alkaline earth metals (Be, Mg, Ca, Sr, Ba, and Ra) are the second most reactive metals in the periodic table, and, like the Group 1 metals, have increasing reactivity with increasing numbers of energy levels. Beryllium (Be) is the only alkaline earth metal that does not react with water, though it reacts with steam if it is heated to high enough temperatures. Additionally, beryllium has a resistant outer oxide layer that lowers its reactivity at lower temperatures.
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Water-reactive substances
Water-reactive substances are those that spontaneously undergo a chemical reaction with water, often noted as generating flammable gas. Some are highly reducing in nature. Notable examples include alkali metals, lithium through caesium, and alkaline earth metals, magnesium through barium.
Some water-reactive substances are also pyrophoric, like organometallics and sulfuric acid. The use of acid-resistant gloves and face shield is recommended for safe handling; fume hoods are another effective control of such substances.
The UN Recommendations on the Transport of Dangerous Goods Model Regulation classifies Water-reactive substances as Class 4.3 (substances which in contact with water emit flammable gases). Countries worldwide have adopted the UN model regulations into their transport of dangerous goods regulations for both international and domestic transportation by road, rail, air and sea. In an NFPA 704 fire diamond's white square, and in similar contexts, they are denoted as "W". The classification of substances as water-reactive is largely a consideration for the safety of firefighting and transportation operations.
All chemicals that react vigorously with water or liberate toxic gas when in contact with water are recognized for their hazardous nature in the "Approved Supply List", or the list of substances covered by the international legislation on major hazards many of which are commonly used in manufacturing processes.
The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table - they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.
The Group 1 metal (M) is oxidised to its metal ions, and water is reduced to hydrogen gas (H2) and hydroxide ion (OH−), giving a general equation of:
The Group 1 metals or alkali metals become more reactive as their number of energy levels increases.
The alkaline earth metals (Be, Mg, Ca, Sr, Ba, and Ra) are the second most reactive metals in the periodic table, and, like the Group 1 metals, have increasing reactivity with increasing numbers of energy levels. Beryllium (Be) is the only alkaline earth metal that does not react with water, though it reacts with steam if it is heated to high enough temperatures. Additionally, beryllium has a resistant outer oxide layer that lowers its reactivity at lower temperatures.