Iron, Ruthenium, Osmium, and Hassium. 
They're transition metals
        
             
        
        
        
Answer:
a) H2SO4 + 2KOH -> 2H2O + K2SO4
b) 9.809 ml
Explanation:
Number of Moles = Mass/ Molar Mass
 Therefore: Mass = Number of moles * Molar Mass
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Molar mass of H2SO4:
H2= 2.02 
S= 32.07
O4= 64
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H2SO4 has the molar mass of 98.09
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the Moles of H2SO4 is given to be 0.100M
Therefore:
Mass= 98.09*0.1
           = 9.809g
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Assuming that 1 g= 1 ml, the volume of sulfuric acid is 9.809 ml.
 
        
             
        
        
        
Answer:
Mass = 18.9 g
Explanation:
Given data:
Mass of Al₂O₃ formed = ?
Mass of Al = 10.0 g
Solution:
Chemical equation:
4Al + 3O₂      →       2Al₂O₃
Number of moles of Al:
Number of moles = mass/molar mass
Number of moles = 10.0 g/ 27 g/mol
Number of moles = 0.37 mol
Now we will compare the moles of Al and Al₂O₃.
                       Al          :          Al₂O₃
                        4           :            2
                      0.37        :         2/4×0.37 = 0.185 mol
Mass of Al₂O₃:
Mass = number of moles × molar mass
Mass = 0.185 mol × 101.9 g/mol
Mass = 18.9 g
 
        
             
        
        
        
The answer is C because the weight is going down so they form a gas.
        
             
        
        
        
Answer: C
Explanation:
In endothermic reactions, enthalpy is positive, and in exothermic reactions, enthalpy is negative, So, if enthalpy is positive, then it is an endothermic reaction, and hence is required for the reaction to occur.