2HCl(aq) + ZnS(s) ⇒ ZnCl₂(aq) + H₂S(g) 
<h3>Further explanation  </h3>
Equalization of chemical reactions can be done using variables. Steps in equalizing the reaction equation:  
- 1. gives a coefficient on substances involved in the equation of reaction such as a, b, or c, etc.  
- 2. make an equation based on the similarity of the number of atoms where the number of atoms = coefficient × index (subscript) between reactant and product  
- 3. Select the coefficient of the substance with the most complex chemical formula equal to 1  
Reaction
HCl(aq) + ZnS(s) ⇒ ZnCl₂(aq) + H₂S(g) 
1. give equation
aHCl(aq) + bZnS(s) ⇒ ZnCl₂(aq) + cH₂S(g) 
2. make an equation
H, left=a, right=2c⇒a=2c(eq 1)
Cl, left=a, right=2⇒a=2⇒c=1(from eq 1)
Zn, left=b, right=1⇒b=1
So the equation :
2HCl(aq) + ZnS(s) ⇒ ZnCl₂(aq) + H₂S(g) 
 
        
             
        
        
        
Answer:
Option (B) 3. 
Explanation:
In the model represented above, the two extreme represent carbon atoms since no other group are attached to it. The joint at the middle also represent carbon atom.
Thus, we can write a more simplify illustration for the model above as
C—C—C
From the above illustration, we can see that the model contains 3 carbon atom. 
 
        
             
        
        
        
Where is the picture to this?