B. the number 3. 
there are 2Al's on both sides and 6 Cl's on the right side so to balance it, you multiply Cl2 by 3 to get 6 Cl's.
        
             
        
        
        
The main idea of an essay is usually portrayed in the thesis.
        
                    
             
        
        
        
The density of Ca will be between that of Mg and Sr
Explanation:
Ca, Mg and Sr are group II elements. They are called alkali earth metals. The correct order of the elements in this group are: Be, Mg, Ca, Sr, Ba and Ra. 
Density is an intensive property of matter which describes the amount of matter(mass) per volume of a substance. 
- Density varies proportionally with mass. The higher the mass, the higher its density. 
- On the periodic table, atomic mass which the number of protons and neutrons in the nucleus of an atom increases down the group. 
- This implies a progradation in the value of density down the group. Therefore one expects that the value of density of Ca will fall between that of Mg and Sr. It cannot be more than 2.6g/cm³ nor less than 1.74g/cm³. 
Learn more: 
density brainly.com/question/2658982
mass number brainly.com/question/2597088
#learnwithBrainly
                     
 
        
             
        
        
        
Answer:
0.40 L
Explanation:
Calculation of the moles of  as:-
 as:-
Mass = 51.24 g
Molar mass of  = 171.34 g/mol
 = 171.34 g/mol
The formula for the calculation of moles is shown below:
 
Thus,
 

Volume = 1.20 L
The expression for the molarity is:


Thus, 
Considering
 
Given  that:
 
 
 
 
So,  
 
 
<u>The volume of 0.24925M stock solution added = 0.40 L
</u>
 
        
             
        
        
        
In earths surface or the bottom of the Ocean