The anode is the negative electrode and so will be donating electrons to assist in this chemical reaction occuring. All reactions accept electrons as reactants. The key issue is the reduction potential Eo (+1.8V). This is greatest for the reaction:
Co3+ + e -> Co2+
Therefore this reaction has the greatest tendency to occur.
Answer is: mass number is 234.
Beta decay is radioactive decay<span> in which a </span>beta ray<span> and a </span>neutrino<span> are emitted from an </span><span>atomic nucleus.
</span>There are two types of beta decay: beta minus<span> and </span>beta plus. <span> In beta minus </span><span>decay, neutron is converted to a proton and an </span>electron<span> and an </span>electron antineutrino and in beta plus <span>decay, a proton is converted to a neutron and </span>positron<span> and an </span>electron neutrino, so mass number does not change.
Answer : The correct answer is 1) AlCl₃ - CH₃Cl 2) HNO₃ -H₂SO₄ at room temperature 3) Fuming HNO₃ -H₂SO₄ at 90-100 ⁰ C heat .
I think this reaction is forming 2,4,6- trinitrotoluene from benzene, since the product is not mentioned. Following are the steps to convert Benzene to 2,4,6 trinitrotoluene .
Step 1: Conversion of Benzene to Toluene .
Benzene can be converted to toluene by Friedel Craft Alkylation of benzene . In this reaction reagent AlCl₃ and Ch3Cl is used . Electrophile CH³⁺ is produced which attached on carbon of benzene and formation of Toluene and HCl occur.

Step 2 : Conversion of Toluene to dinitrotoluene.
Dinitritoluene is prepared from toluene by Nitration . This reaction uses Electrophilic substitution mechanism . The reagents used are HNO₃ and H₂SO₄ at room temperature . These reagents produces NO₂⁺ ( nitronium ion ), a electrophile which attacks on C2 and C4 Carbon atoms of Toluene.
Toluene 
Step 3) Conversion of Dinitro toluene to trinitrotoluene.
This reaction is extended nitration of toluene . Further nitration is done in extreme condition . The temperature of reaction is increased to 90- 100 ⁰ C . Due to which there is more production of NO²⁺ ion occurs from HNO₃ -H₂SO₄ and they attack on C6 carbon atom of dinitrotoluene which forms 2,4,6- trinitrotoluene.
Dinitrotoluene 
So over all reaction uses three reagents in order :

The top number on elements in the periodic table is the atomic number, so when you look at the periodic table you can see that 42 is Mo (Molybdenum), and this is the only element with that atomic number.
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