Answer:
a molecule with two of the same element
Explanation:
 
        
             
        
        
        
Atomic mass Calcium ( Ca) = 40.078 u.m.a
40.078 g --------------- 6.02x10²³ atoms
187 g ------------------- ??
187 x ( 6.02x10²³) / 40.078 =
1.125x10²⁶ / 40.078 = 2.808x10²⁴ atoms
hope this helps!
        
             
        
        
        
The answer is d, hand soap. 
Hand soap is alkaline and red litmus paper turns blue when exposed to alkaline solution.
        
             
        
        
        
When calcium carbonate is heated, it breaks down to form calcium oxide and carbon dioxide.
Thermal decomposition is the process in which heat is required.
It is also known as thermolysis.
It is processed in which a compound breaks into two or more products when the heat is supplied.
This reaction is used for the production of oxygen.
This reaction is also used for production of acidic as well as basic oxides.
CaCO3 on thermal decomposition gives:
CaCO3→CaO+CO2
CaO→ Basic oxide.
CO2→ Acidic oxide.
 
        
             
        
        
        
When hydrogen peroxide is broken down the gas released or given off is Oxygen.