Answer - A substance is matter that has a uniform and definite composition. All samples of substances, sometimes called pure substances, have identical properties.
        
             
        
        
        
Answer:
0.32M
Explanation:
Given parameters: 
Number of moles of NaCl  = 1.29moles 
Volume of solution = 4liters  = 4dm³
Unknown: 
Molarity of solution = ? 
Solution: 
Molarity is one the ways of expressing the concentration of a solute in a solution. It is given as; 
          Molarity  = 
The unit is given as M which is mol/dm³
     Input the parameters and solve; 
            Molarity  =  = 0.32mol/dm³ or 0.32M
    = 0.32mol/dm³ or 0.32M
 
        
             
        
        
        
Answer:
A. 28 years
Explanation:
Applying,
R = R'(2ᵃ/ⁿ).............. Equation 1
Where R = Original sample, R' = Sample left after decay, a = Total time taken to decay, n = half life.
From the question,
Given: R = 12 g, R' = 6 g, a = 28 years.
Substitute into equation 1 and solve for n
12 = 6(2²⁸/ⁿ)
12/6 = 2²⁸/ⁿ
2²⁸/ⁿ = 2
Equation the base,
28/n = 1
n = 28 years.
Hence the half-life is 28 years
 
        
             
        
        
        
It would cause a drop <span>but I am not sure  double check other answers </span>