Answer:
pOH = 4.8 
pH = 9.2
Explanation:
Given data:
Hydrogen ion concentration = 6.3×10⁻¹⁰M
pH of solution = ?
pOH of solution = ?
Solution:
Formula:
pH = -log [H⁺]
 [H⁺] = Hydrogen ion concentration
We will put the values in formula to calculate the pH.
pH = -log [6.3×10⁻¹⁰]
pH = 9.2
To calculate the pOH:
pH + pOH = 14
We will rearrange this equation.
pOH = 14 - pH 
now we will put the values of pH.
pOH = 14 - 9.2
pOH = 4.8 
 
        
             
        
        
        
Sun to kelp 
kelp to sea urchin
sea urchin to otter 
otter to shark 
kelp,sea urchin,otter,shark to bacteria 
bacteria back to kelp
 
        
             
        
        
        
Answer:
D)groups 1 and 2 
Explanation:
The s-block of elements are made up of those chemical elements we can find in groups 1 and 2 on the periodic table. 
A periodic table of element is based on the periodic law which states that "the properties of elements are a periodic function of their atomic number". 
In the table; 
- elements having the same number of electrons in the outermost shell are placed over one another in vertical columns. 
- each resulting vertical column is called a group or family.
- resulting horizontal rows are known as periods.  
The s-block consists of elements in groups 1 and 2 having an outermost ""ns"" shell configuration. They are predominantly metals. 
For Option A, groups 3-12 is the D-block
Option B, group 18 is filled with noble gases and it makes up the p-block
Option C, group 13-18 is makes up the p-block too. 
So, the s-block is made up group 1 and 2 elements. 
 
        
             
        
        
        
Endo is more in reactants and exo is more in products because in exothermic reactions heat is released