Answer:
Diamond
Explanation:
Diamond has covalent bonds, which makes it a non-metal. 
However, it also has a tetrahedral structure, which holds its C atoms together by strong forces, thus making it hard.
Diamond also has free-moving electrons due to its tetrahedral structure, thus making it possible to conduct electricity.
 
        
             
        
        
        
Answer:
C- A proton has about the same mass as a neutron .
Explanation:
In an atom such as a carbon atom, the masses of the proton and neutrons are the same. 
The mass of the electrons is very negligible. 
- Protons are the positively charged particles in an atom
- Neutrons do not carry any charges 
- Both protons and neutrons have similar masses. 
- They contribute the bulk of the mass of the atom. 
- The electrons carry negative charges and they have negligible masses. 
The mass of protons and neutrons are similar. 
 
        
             
        
        
        
Answer:
finding the mass percentage oven element in a compound might sound complicated, but the calculation is simple. For example, to determine the mass percentage of hydrogen in water H2O, divide the major mass of hydrogen by the total molar mass of water and then multiply the result by 100
 
        
             
        
        
        
Answer:
Number of moles = 0.0005 mol.
Explanation:
Given data:
pH = 3
Volume of solution = 500 mL
Number of moles = ?
Solution:
HCl dissociate to gives H⁺ and Cl⁻
HCl → H⁺ + Cl⁻
It is known that,
pH = -log [H⁺]
3 = -log [H⁺]
[H⁺] = 10⁻³ M
[H⁺] = 0.001 M
Number of moles of HCl:
Molarity = number of moles / Volume in litter
Number of moles = Molarity × Volume in litter
Number of moles = 0.001 mol/L × 0.5 L
Number of moles = 0.0005 mol
 
        
             
        
        
        
The redox reaction is
 
Here
Calcium undergoes reduction, and acts as cathode
Lithium undergoes oxidation and acts as anode
The reduction potential of calcium is -2.87 V
The reduction potential of lithium is - -3.05 V
We know that
Ecell = Ecathode - Eanode
Ecell = -2.87 - (-3.05)  = 0.18 V