18.5 Occurrence, preparation, and compounds of hydrogen  (Page 6/9)

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Hydrofluoric acid is unique in its reactions with sand (silicon dioxide) and with glass, which is a mixture of silicates:

${\text{SiO}}_{2}\left(s\right)+\text{4HF}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{SiF}}_{4}\left(g\right)+{\text{2H}}_{2}\text{O}\left(l\right)$
${\text{CaSiO}}_{3}\left(s\right)+\text{6HF}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{CaF}}_{2}\left(s\right)+{\text{SiF}}_{4}\left(g\right)+{\text{3H}}_{2}\text{O}\left(l\right)$

The volatile silicon tetrafluoride escapes from these reactions. Because hydrogen fluoride attacks glass, it can frost or etch glass and is used to etch markings on thermometers, burets, and other glassware.

The largest use for hydrogen fluoride is in production of hydrochlorofluorocarbons for refrigerants, in plastics, and in propellants. The second largest use is in the manufacture of cryolite, Na 3 AlF 6 , which is important in the production of aluminum. The acid is also important in the production of other inorganic fluorides (such as BF 3 ), which serve as catalysts in the industrial synthesis of certain organic compounds.

Hydrochloric acid is relatively inexpensive. It is an important and versatile acid in industry and is important for the manufacture of metal chlorides, dyes, glue, glucose, and various other chemicals. A considerable amount is also important for the activation of oil wells and as pickle liquor—an acid used to remove oxide coating from iron or steel that is to be galvanized, tinned, or enameled. The amounts of hydrobromic acid and hydroiodic acid used commercially are insignificant by comparison.

Key concepts and summary

Hydrogen is the most abundant element in the universe and its chemistry is truly unique. Although it has some chemical reactivity that is similar to that of the alkali metals, hydrogen has many of the same chemical properties of a nonmetal with a relatively low electronegativity. It forms ionic hydrides with active metals, covalent compounds in which it has an oxidation state of 1− with less electronegative elements, and covalent compounds in which it has an oxidation state of 1+ with more electronegative nonmetals. It reacts explosively with oxygen, fluorine, and chlorine, less readily with bromine, and much less readily with iodine, sulfur, and nitrogen. Hydrogen reduces the oxides of metals with lower reduction potentials than chromium to form the metal and water. The hydrogen halides are all acidic when dissolved in water.

Chemistry end of chapter exercises

Why does hydrogen not exhibit an oxidation state of 1− when bonded to nonmetals?

The electronegativity of the nonmetals is greater than that of hydrogen. Thus, the negative charge is better represented on the nonmetal, which has the greater tendency to attract electrons in the bond to itself.

The reaction of calcium hydride, CaH 2 , with water can be characterized as a Lewis acid-base reaction:
${\text{CaH}}_{2}\left(s\right)+{\text{2H}}_{2}\text{O}\left(l\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{Ca}{\left(\text{OH}\right)}_{2}\left(aq\right)+{\text{2H}}_{2}\left(g\right)$

Identify the Lewis acid and the Lewis base among the reactants. The reaction is also an oxidation-reduction reaction. Identify the oxidizing agent, the reducing agent, and the changes in oxidation number that occur in the reaction.

In drawing Lewis structures, we learn that a hydrogen atom forms only one bond in a covalent compound. Why?

Hydrogen has only one orbital with which to bond to other atoms. Consequently, only one two-electron bond can form.

What mass of CaH 2 is necessary to react with water to provide enough hydrogen gas to fill a balloon at 20 °C and 0.8 atm pressure with a volume of 4.5 L? The balanced equation is:
${\text{CaH}}_{2}\left(s\right)+{\text{2H}}_{2}\text{O}\left(l\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{Ca}{\left(\text{OH}\right)}_{2}\left(aq\right)+{\text{2H}}_{2}\left(g\right)$

What mass of hydrogen gas results from the reaction of 8.5 g of KH with water?
$\text{KH}+{\text{H}}_{2}\text{O}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{KOH}+{\text{H}}_{2}$

0.43 g H 2

can someone please tell me what does an Entropy means
what is chemistry?
what is chemistry
Afiwape
chemistry is a brach of science which deal with the study of the nature, composition structure and with the force that hold the structure together and the change matter will undergo undedifferent conditions
Afiwape
And god has created everything from nothing
Abdelkarim
forms of biotechnology
What is a mole?
pls give me 3 type of transition metal
Copper, Scandium, Vanadium, Iron, Chromium, Cobalt
Jumaane-Kalif
ion zinc hydrogen
Abdul
that is not true
Jumaane-Kalif
stop posting foolishness
Jumaane-Kalif
how do I name compounds
depends on the compound. as you may know there's transition metal compounds and there's organic compounds and so on and so forth.
Jumaane-Kalif
what is electricity
electricity refers to the flow electrons
John
Hi. please can you tell me more on chemical equation
When 1 or 2 chemicals react, they rearrange their atomic composition forming new compounds. The total mass before and after is the same/ constant. Chemical equations of same reactants react in same ratios e.g. 1 Na ion reacts with 1 water molecule or a multipier like 1 mole of Na ions react with 1
Abdelkarim
Mole of water molecules. In that example we multipied by 6.02*10^23 or avogadro constant (L). Or 2 Na+ ions with two water molecules. The arrow means '' to form '' Some times conditions or reactants are written above the arrow like H+ or enzyme or temper, sometimes physical states are written
Abdelkarim
Beside the chemical Aqueous (aq) which means solute dissolved on water. Solid (s) etc Some chemical equations are written next to it ΔH= # which means enthalpy change which describes if the reaction is endothermic (+) or exothermic (-).
Abdelkarim
Some are reversible and have half double arrow sign.
Abdelkarim
what is the meaning of atoma
what is theory
what is chemical compound
Lorrita
A compound is the result of chemical bonding between 2 or more different elements.
Abdelkarim
Why is an atom electrically neutral?
Clara
the same number of electron , proton present in an atom.thats why it is electrically neutral
debibandita
difference between Amine and amide
what is the difference between alkanal and alkanone
difference between alkanol and alkanal
Michael
whaatt
Saturday
you are not well at all
Ibrahim
is organic compounds used for drying agent
Sulfuric acid is used as a drying agent.
Abdelkarim
what is an atom
An atom is the smallest part of an element, for instance gold atoms are the smallest part of gold that can enter a reaction. An atom must consist protons and electrons of equal number. You can think of those subatomic particles as spheres, but not orbiting randomly they move in specific way in
Abdelkarim
That was partially described mathematically. As a muslim, we believe that god created all matter from nothing. He is the Able, and only who can create matter in the begging in the big bang that was described in the Quran in chapter 17 verse 30, 1400 years ago, you can read it from internet.
Abdelkarim
what is electron affinity
John
do you have a private jet
Ibrahim
what is acid
Proton donor (H+). Like in lemons, oranges and some medicines.
Abdelkarim
what is titration? and how can i get my readings?