Answer:
Water, air, and food.
Explanation:
All living things need air water and food to live.
Answer is: nickel (Ni) is the most active metal.
Chemical reaction 1: Pb(NO₃)₂(aq) + Ni(s) → Ni(NO₃)₂(aq) + Pb(s).
Chemical reaction 2: Pb(NO₃)₂(aq) + Ag(s) → no reaction.
Chemical reaction 3: Cu(NO₃)₂(aq)) + Ni(s) → Ni(NO₃)₂(aq) + Cu(s).
From chemical reactions 1 and 3, we can conclude that nickel is more reactive than lead (Pb) and copper (Cu), because lead is more reactive than silver (Ag), chemical reaction 2, nickel is also more reactive than silver.
In chemical reaction 2, no reaction occurs because silver is less reactive than lead. Lead is higher in activity series of metals and can not be reduced.
Nickel is higher in activity series of metals than lead, copper and silver.
The activity series is a series of metals from highest to lowest reactivity. Metal higher in the reactivity series will displace another.
Concept: According to the basic concept of the electronic configuration of the element, the electron can be filled first in those shell which has least energy or (n +l) value. Here, n is the principal quantum number on shell and l is the azimuthal quantum number.
Since, the first shell has least value of energy in any atom. So, it should be filled first.
Hence, the correct statement can be written as;
When diagramming an atom, the electron shells _nearest to _ the nucleus must be filled first.
Answer:
∆H > 0
∆Srxn <0
∆G >0
∆Suniverse <0
Explanation:
We are informed that the reaction is endothermic. An endothermic reaction is one in which energy is absorbed hence ∆H is positive at all temperatures.
Similarly, absorption of energy leads to a decrease in entropy of the reaction system. Hence the change in entropy of the reaction ∆Sreaction is negative at all temperatures.
The change in free energy for the reaction is positive at all temperatures since ∆S reaction is negative then from ∆G= ∆H - T∆S, we see that given the positive value of ∆H, ∆G must always return a positive value at all temperatures.
Since entropy of the surrounding= - ∆H/T, given that ∆H is positive, ∆S surrounding will be negative at all temperatures. This is so because an endothermic reaction causes the surrounding to cool down.
