lecture 5 Flashcards
Why does H+ not exist in nature?
Because its ioniziation energy is high enough.
what are isotopes?
isotopes have different mass number but share the same atomic number.
are the differences in isotopes in chemical or physical properties? explain.
physical properties. since the difference is in the mass number of the atom.
What are the isotopes of hydrogen?
protium [H]
deuterium [D]
tritium [T]
where does tritium exist?
the upper atmosphere and found naturally in space.
what are the rays that radioactive tritium emit?
weak beta rays emitter
why is hydrogen not in the alkali metal group or in the halogen group?
it is not a metal and doesn’t react with water. rarely forms non-negative ion and is reactive comparatively.
why do some people think hydrogen belongs in alkali metal group or halogen group?
forms mono-positive ions, has a single s electron.
is a non-metal. forms diatomic molecule.
what are the types of hydrogen based off of rotation?
ortho-hydrogen which is stable.
para-hydrogen which is less stable.
how to prepare small quantities of hydrogen?
- electrolysis of water that has extra electrolytes.
- reacting dilute acid and suitable metals.
- treating a metal that forms amphoteric hydroxides with aqueous alkali.
- reacting metal hydrides with water.
example for dilute acid and metal to make hydrogen
Zn + 2 HCl -> ZnCl2 + H2
example of treating metal to form amphoteric hydroxides with aqueous alkali.
2 Al + 2 NaOH + 6 H2O -> 2 Na[Al(OH)4]
example reacting metal hydrides with water.
CaH2 + 2 H2O -> Ca(OH)2 + 2 H2
how is dihydrogen commercially produced?
steam reformer process.
what is the steam reformer process?
red hot cakes + steam -> water gas -(catalyst)-> Co2 + H2
chemical equations for forming hydrogen.
CH4 + H2O -[nickel catalyst]-> CO2 + H2O
=> CO + 2H2 -[copper/zinc oxide catalyst]-> CH3OH
or
=> CO2 + 3H2 -[copper/zinc oxide catalyst]-> CH3OH + H2O
reactivity of hydrogen. explain
not reactive in ambient conditions. due to the strength of the H-H bond.
combustion of hydrogen. give example
burns with a pale blue flame.
2 H2 + O2 -> 2 H2O
hydrogen reacting with nitrogen write chemical equation.
makes ammonia. 3 H2 + N2 -> 2 NH3
hydrogen reacting with oxygen
makes water gas. 2 H2 + O2 -> 2 H2O
hydrogen reacting with reactive metals.
Ca + H2 -[525k]-> CaH2
hydrogen reacting with metals.
makes interstitial hydrides.
hydrogen reacting with metal oxides. give example.
less active.
FeO4 + 4 H2 -[heat]-> 3 Fe = 4 H2O
CuO +H2 -[heat]-> Cu + H2O
hydrogen reacting with metal oxides. give example.
less active.
FeO4 + 4 H2 -[heat]-> 3 Fe + 4 H2O
CuO +H2 -[heat]-> Cu + H2O
hydrogen reacting with metal oxides. give example.
less active.
FeO4 + 4H2 -[heat]-> 3Fe = 4H2O
CuO +H2 -[heat]-> Cu + H2O
what is a hydrogen bond?
bond created between hydrogen atom and electronegative atom or an electronegative atom with lone pair.
what affects boiling and melting point in water?
hydrogen bond. due to the intermolecular forces.
what role does hydrogen play in the existence of life?
close to carbon in electronegativity.
The ability to form hydrogen bonds.
Chemical equatuon for preparing hydrogen peroxide.
Na2O2 + H2SO4 -> Na2SO4 + H2O2
Equation to prepare hydrogen peroxide from barium peroxide
BaO2 + 8 H2O + H2SO4 -> BaSO4 + 8 H2O + H2O2
What is hydrogen peroxide used for?
Bleaching. Rocket fuel. Sold as perhydrol.
What are hydrides?
Binary compounds of hydrogen.
What are ionic hydrides made of?
Metal cation and hydride ion.
Propeties of ionic hydrides?
White solid. Very reactive. Reducing agent.
example of hydrides.
LiH + H2O2 -> LiOH + H2
CaH2 + N2O -> Ca(OH)2 + H2
what are covalent hydrates?
non-metal and weakly electropositive metal.
properties of covalent hydrides
gas at room temperature.
what type of intermolecular forces in hydrides?
only has London dispersion forces due to its low polarity.
example of covalent hydrides.
CH4 + 2 O2 -> CO2 + 2 H2O
what are metallic hydrides?
it’s when hydrogen atoms are found in the interstitial space in metals.
properties of metallic hydrides.
non-stiometric. less dense. brittle. lower connectivity.
give an example of where metallic hydrides are used.
battery technology. nickel-metal-hydride cell.
what are obstacles in the hydrogen economy?
transportation
formation of water.
uses of hydrogen
reducing agent. hydrogenated vegetable oil. melding rocket fuel.
