Answer:
Cl
Explanation:
 chlorine (2,8,7) is a non metal with highest electronegativity. Hence, it is most likely to form a negative ion with charge −1. 
I hope it helps you
 
        
             
        
        
        
Complete Question 
You determine that it takes 26.0 mL of base to neutralize a sample of your unknown acid solution. The pH of the solution was 7.82 when exactly 13 mL of base had been added, you notice that the concentration of the unknown acid was 0.1 M. What is the pKa of your unknown acid?
Answer:
The pK_a value is  
 
Explanation:
From the question we are told 
     The volume of base is  
      The pH of solution is  
       The concentration of the acid is 
From the pH we can see that the titration is between a strong base and a weak acid 
  Let assume that the the volume of acid is  
 Generally the concentration of base 
                     
 Substituting value  
                      
                     
When 13mL of the base is added a buffer is formed 
The chemical equation of the reaction is 
            
Now before the reaction the number of mole of base is  
             ![No \ of \ moles[N_B]  =  C_B * V_B](https://tex.z-dn.net/?f=No%20%5C%20of%20%5C%20moles%5BN_B%5D%20%20%3D%20%20C_B%20%2A%20V_B)
Substituting value  
                     
                           
     
                                  
Now before the reaction the number of mole of acid is  
             
Substituting value  
                     
                          
Now after the reaction the number of moles of  base is  zero  i.e has been used up 
     this mathematically represented as 
                          
     The  number of moles of acid is  
              
                    
 The pH of this reaction can be mathematically represented as 
                  ![pH  = pK_a + log \frac{[base]}{[acid]}](https://tex.z-dn.net/?f=pH%20%20%3D%20pK_a%20%2B%20log%20%5Cfrac%7B%5Bbase%5D%7D%7B%5Bacid%5D%7D)
 Substituting values 
                   
                    
        
                      
               
                                  
         
            
                       
 
        
             
        
        
        
Answer:
May be the instrument is incorrect or may be error in it.
Explanation:
The copper have not been detected by this test because the test may be not for the detection of copper, may be it is used for identification of another minerals. If there is copper in the lake sample but can't be detected in the test so it means that the instrument which is used for detection is not the right one  or having error in that instrument. Every mineral has a specific type of instrument that detect its presence, if we use incorrect instrument for the mineral then we can't detect the presence of that specific mineral.
 
        
             
        
        
        
Because the reactants react with each other and chemically react to produce a different product like with fire when it reacts with the wood it burns and the product left behind is a new different substance from the reactants in this case the product is ash
        
                    
             
        
        
        
Answer:
The volume of the sample is 17.4L
Explanation:
The reaction that occurs requires the same amount of CO and NO. As the moles added of both reactants are the same you don't have any limiting reactant. The only thing we need is the reaction where 4 moles of gases (2mol CO + 2mol NO) produce 3 moles of gases (2mol CO2 + 1mol N2). The moles produced are:
0.1800mol + 0.1800mol reactants = 
0.3600mol reactant * (3mol products / 4mol reactants) = 0.2700 moles products.
Using Avogadro's law (States the moles of a gas are directly proportional to its pressure under constant temperature and pressure) we can find the volume of the products:
V1n2 = V2n1
<em>Where V is volume and n moles of 1, initial state and 2, final state of the gas</em>
Replacing:
V1 = 23.2L
n2 = 0.2700 moles
V2 = ??
n1 = 0.3600 moles
23.2L*0.2700mol = V2*0.3600moles
17.4L = V2
<h3>The volume of the sample is 17.4L</h3>