I think the correct answers from the choices listed above are the first, third and the last option. Ionic compounds are compounds that dissociates into ions when in aqueous solution. From the list, NH4Cl, KF and MgO are the ionic compounds. Hope this answers the question.
        
                    
             
        
        
        
The final temperature of the mixture : 21.1° C  
<h3>Further explanation  </h3>
The law of conservation of energy can be applied to heat changes, i.e. the heat received / absorbed is the same as the heat released  
Q in(gained) = Q out(lost)  
Heat can be calculated using the formula:  
Q = mc∆T  
Q = heat, J  
m = mass, g  
c = specific heat, joules / g ° C  
∆T = temperature difference, ° C / K  
Q ethanol=Q water
mass ethanol= 

mass water =

then the heat transfer :

 
        
             
        
        
        
German scientist Döbereiner was one responsible for grouping elements into triads based on most notably atomic mass, many of which can be found in the periodic table to be in a pattern (for example <span><span>Iron </span><span>Cobalt </span><span>Nickel, elements 26, 27, 28)</span></span>
        
                    
             
        
        
        
Answer:
A:UNDERSTANDING CONCEPTS PART A 13) Which of the following is an example of periodicity? A) eating breakfast
 
        
             
        
        
        
The five main branches of chemistry are organic chemistry, inorganic chemistry, analytical chemistry, physical chemistry and biochemistry. Chemistry can be further divided into many sub-branches that may fall under more than one of the main branches.