A.) baking soda is the answer
        
             
        
        
        
Answer:
0.171 grams of oxygen combined with the metal.
Explanation:

Mass of magnesium oxide produced = 0.421 g
Mass of magnesium metal used = 0.250 g
Suppose reaction completely converts the magnesium into magnesium oxide.
Mass of oxygen combined with magnesium = m
 0.421 g = 0.250 g + m
m =  0.421 g - 0.250 g = 0.171 g
0.171 grams of oxygen combined with the metal.
 
        
             
        
        
        
Answer:
Welp God made everything so that means the big bang never happened so that means techniqually the answer to your question is nothing ig. 
hope this helps
 
        
             
        
        
        
Answer:
*2Kl+Pb(NO3)2=PbI2+2KNO3: double replacement.
*2Al+3CuSO4=Al2(SO4)3+3Cu: single replacement.
*C2H5OH+3O2=2CO2+3H2O: combustion.
Explanation:
Hello there!
In this case, according to the required, it turns out necessary for us to recall the five types of reactions, combination, decomposition, single and double replacement and combustion as shown on the attached figure.
In such a way, since the first reaction follows the pattern AB+CD-->AD+CB we infer it is double replacement; the second reaction follows the patter A+BC-->AC+B and therefore it is single replacement; and the last one follows the pattern of combustion reaction due to the presence of CO2 and H2O on the products side.
Regards!