Na is cation so it loses electron to be positive and become stable losing one valence shells one electron so it's oxidation number is +1 ie A is correct
The simplified model of the hall effect proved that the current (electric) in metals are carried by electrons and not protons. The hall effect introduced the hall coefficient which is the ratio of the induced electric field to the current density x applied magnetic field. This coefficient is unique for each type of metal.
Answer:
For temperatures higher than 533.49 K we will see a spontaneous reaction, and for temperatures lower than that the reaction will not be spontaneous.
Explanation:
When are chemical reactions spontaneous? To find out we need to look at the reaction's change in Gibbs Free energy:
When this is greater than zero, the reaction isn't spontaneous, when it is less than zero, we have a spontaneous reaction. The reaction must then change from spontaneous to non spontaneous when 
. If we insert that into our equation we get:
That is the temperature at which the reaction's spontaneity will change, plugging in our values we find:
At that temperature we have .
Now, at a temperature greater than this one, the entropy term in our equation for the Gibbs' free energy of reaction will take over, and make 
, thus the reaction will be spontaneous.
On the other hand, if we lower the temperature, we will have a smaller entropy term, and we will have: 
. That is, the reaction will not be spontaneous. Therefore for temperatures higher than 533.49 K we will see a spontaneous reaction, and for temperatures lower than that the reaction will not be spontaneous.
Answer:
Three of the five oxides are expected to form acidic solutions in water
Explanation:
We have different types of oxides : Acidic oxides, Basic oxides, Amphoteric oxides, Peroxides and Higher oxides.
Only acidic oxides will dissolve in water to give an acidic solution.
Considering the given oxides carefully,
- SO2 will dissolve in water to produce H2SO3 which is acidic.
- Y2O3 will dissolve in water to produce Yttrium(III) hydroxide which is basic.
- MgO will dissolve in water only to produce Mg(OH)2 which is also basic.
- Cl2O dichlorine mono oxide will dissolve in water to produce HClO which is acidic.
- N2O5 will dissolve in water to produce HNO3 which is also acidic.
