Answer:
A
Explanation:
The first option is the only option where new products are formed.
In the D option no new product is formed.
Same goes with option C.
In B no new products are formed.
Change is said to be taken place only with formation of new products from reactants.
Redox
reactions are those in which the oxidation numbers of the elements involved are
changed.
Equation
1:
2Na(s)
+ Cl2(g) --> 2NaCl
The
oxidation numbers of Na and Cl in the reactant side are both zero because they
are in elemental form. In the product side, however, the oxidation numbers are
+1 and -1, respectively. Hence, this is an example of redox reaction.
Equation
2:
Cd(s)
+ Pb+2(aq) --> Cd2+(aq) + Pb(s)
The
oxidation numbers of Cd and Pb+2 in the reactant side are 0 and +2,
respectively. They are, however, +2 and 0 in the product side. Hence, this is
also a redox reaction.
Equation
3:
Pb(NO3)2(liq)
+ 2LiCl(aq) --> PbCl2(s) + 2LiNO3(aq)
The
oxidation numbers of the involved ions (both cations and anions) are not
changed. Hence, this is NOT an oxidation reaction.
Equation
4:
C(s)
+ O2(g) --> CO2(g)
Just
as the equation 1 and 2, the oxidation numbers of the reactants are not similar
to those in the product. Hence, this is an example of oxidation reaction.
Answer:
0.00782 mol Pb
Explanation:
There are always 6.02 × 10²³ atoms in 1 mole of an element.
4.71 × 10²¹ atoms Pb × (1 mol Pb ÷ 6.02 × 10²³ atoms) = 0.00782 mol Pb
This is a chemical property due to radioactivity being a chemical characteristic of uranium. This fact describes its chemical structure.
Far apart and have weak attractive forces between them
