The heat of combustion of carbon to CO2 is -393.5 kJ/ mol. The heat released upon formation of 35.2 gm of CO2 from carbon and oxygen gas is:
+315 kJ
-31.5 kJ
-315 kJ
+31.5 kJ
Which of the following substances acts as an oxidising as well as a reducing agent ?
Na2O
SnCl2
Na2O2
NaNO2
3ClO-(aq) → ClO- + 2Cl is an example of
Oxidation reaction
reduction reaction
disproportionation reaction
decomposition reaction
In the equation
CrO + SO
the oxidation number of Cr changes from
+6 to +4
+6 to +3
+8 to +4
+4 to +3
Which quantities are conserved in all oxidation- reduction reactions?
Charge only
Mass only
Both charge and mass
Neither charge nor mass
C.
Both charge and mass
Oxidation involves loss of electrons and reduction involves gain of electrons, hence in case of oxidation-reduction reactions (redox reactions) charge remains conserved. Moreover, in all chemical reactions mass also remains conserved. eg, in the reaction,
Silver metal is recovered industrially by using the chemistry shown below. Which of the following statements is/are not true?
2K[Ag(CN)2] +Zn→ K2[Zn(CN)4] + 2Ag
only Ag has been oxidised and Zn reduced
(a), (c), (d)
Both Ag and Zn have been oxidised
Both Ag and Zn have been reduced
Which of the following does not/do not represent the correct equivalent mass of Cr2O in the reaction Cr2O+ 14 H+ + 6e- → 2Cr3+ + 7H2O.
The molar mass of dichromate
One third of the molar mass of dichromate
One half of the molar mass of dichromate
all of the above