Unit 8 Oxidation reduction rxns
which takes place during a redox rxn?
electrons are both gained and lost
the oxidation number of hydrogen when it is in a compound other than a hydride____?
+1
the oxidation number of sulfur in each of the following is +6 except____?
S2O4 2-
the oxidation number of bromine in bromine gas is____?
0
which coefficient of H+ balances the atoms in this half reaction? H+ +MnO2---->Mn2+ +H2O
4
what is the coeffiicient of H2when you balance the equation for this redox reaction.
7
Which atom has a change in oxidation number of -3 in the following redox reaction? K2Cr2O7 + H2O +S→KOH + Cr2O3 + SO2
Cr
what is the reduction half reaction for this unbalanced redox equation? Cr2O7...
Cr2O7-+NH4---->Cr2O3
which substance is reduced in this redox reaction? CuO+H2---->Cu+H2O
Cu
what is the oxidation half reaction for this unbalanced redox reation? Cr2O7+Fe2+ __------->Cr3+Fe3+
Fe2+----->Fe3+
in which substance does chlorine have an oxidation number of +5?
KClO3
identify the atom that increases in oxidation number in this redox rxn: 2MnO2+2K2CO3+O2---->2KMnO4+2CO2
Mn
wha tis the ionic form of this unbalanced equation? MnO2+HNO2---->Mn(NO3)2+H2O
MnO2+ H+ +NO2- -------->Mn2+ +NO3- +H2O
what is the oxidation number for each atom in NH4Cl?
N=-3, H=+1, Cl=-1
in which of the following compounds is the oxidation number of nitrogen different from the other three?
NH4Cl
oxidation is____?
a loss of electrons
Cu---->Cu2+2e- this equation represents____?
an oxidation rxn
which pair of substances might be involved in an O.R rxn that would result in the formation of ions
aluminum and oxygen
which is the first step to follow when using the oxidation number change method to balance a redox equation?
assign oxidation numbers
in this unbalance rxn, which atom is oxidized? HNO3+HBr---->NO+Br2+H2O
bromine
in the rxn between bromine and sodium, a bromine atom gains an electron and forms the bromide ion Br-. what happens to bromine?
bromine is reduced
in this unbalance rxn, which atom is reduced? H2O+Cl2+SO2---->HCl+H2SO4
chlorine
in the reaction of calcium with chlorine____? chlorine takes electrons reduction
chlorine is oxidizing agent
which statement is true about the following rxn? S+Cl2---->SCL2
chlorine is reduced to SCl2
what is the name of the following process? 2Fe.. 4Fe./.
corrosion
in the rxn of Hydrogen with iodine____?
hydrogen is oxidized
which element increases its oxidation number in this rxn? 3KOH+H3PO4---->K3PO4+3H2O
no element increases its oxidation number
this unbalanced equation describes a redox rxn. what is the total increase in oxidation number of the species being oxidized? Fe and CO2's
+6 Fe
what is the oxidation number of oxygen in the nitrate NO3-
-2
the oxidation number of magnesium in magnesium chloride is____?
2
what is the coefficient of MnO2 when you balance the equation for this redox reaction. KCN...
2
What is the balanced equation for this reaction, which takes place in a basic solution? Cr(OH)3(s) + ClO3-(aq) → CrO42 (aq) + Cl-(aq)
2Cr(OH)3(s) + ClO3-(aq) + 4OH-(aq) → 2CrO42-(aq) + Cl-(aq) + 5H2O(l)
which of the following is a reduction half-reaction?
2H+ + 2e- --> H2
When the half-reactions Br2 +2e- → 2Br- and Na → Na+ +e- are combined, the balanced redox equation is _____
2Na + Br2 → 2Na+ + 2Br-
which substance has a coefficient of 2 when you balance the equation for this redox reaction Cu+HNO3--->Cu(NO3)2+NO+H2O
NO
what is the reducing agent in the following rxn 2Na+2H20---->2NaOH+H2
Na
what is the reducing agent in the following rxn 2Na+S---->Na2S?
Na
A certain redox reaction takes place in a basic solution. which species must you include to balance for this reaction
OH
whic of the following is a oxidation half-reaction?
SN2+---->SN4+ +2e
what are transfered in a O.R rxn?
electrons
which element decreases its oxidation # in this rxn I2+2KCl---->2Kl+Cl2
iodine
which O.R rxns are best balanced by the half rxn method?
ionic rxns
during a chemical rxn, an iron atom became the ion Fe2+. what happened to the iron atom
it lost electrons and was oxidized
which element decreases in its oxidation number in this rxn? BiCl2+Na2SO4---->2NaCl+BiSO4
no element decreases its oxidation number
which of the following rxns is a redox rxn?
not acid base
which type of rxn does Sn2+---->Sn4+ represent
oxidation
what is shown by a half rxn?
oxidation or reduction of an element
in the rxn with sodium and oxygen____?
oxygen is reduced
why is oxygen reduced in teh reaction of hydrogen with oxygen to make water?
oxygen pulls electrons towards itself
in which type of rxn are electrons gained?
reduction
what happens to iron when iron oxide becomes elemental iron?
reduction
equations for which kinds of rxns are best balanced by the half rxn method?
rxns that take place in acidic solutions
which of the following is a redox reaction?
single replacement
which element increases its oxidation number in this rxn?2Na+2H20---->2NaOH+H2
sodium
in the rxn with sodium and oxygen____?
sodium is the reducing agent
iron corrodes because ___ turns iron into ions through the process of____?
water, oxidation
