Answer: 1.24 × 10^25
Explanation:
 ×
 × 
Using our knowledge in unit conversions, we know the mole units cancel each other out and all there's left is the atom unit. From here we can multiply the fractions and eventually we end with the number 124.0532 × 10^23
According to the scientific notation rules, the number to the left of the decimal cannot exceed 10 so we have to move the decimal to the left two spaces. With this change, we also have to change the exponent of the 10. Because we moved the decimal point two spaces to the left, that means we have 10^25.
 
        
             
        
        
        
Ba 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s² → [Xe]6s²
Ba - 2e⁻ → Ba⁺²  [Xe]
        
                    
             
        
        
        
Answer: % Errror = 11.05%
Explanation:
Percentage error is the difference between the measured value and the theoretical value as expressed in percent. 
That is; 
% Error =
( Theoretical value -measured value) /(Theoretical value) × 100
Theoretical value =55.2kJ
Measured value = 49.1kJ
% Error = (55.2-49.1)/(55.2) ×100
%Error = 6.1/55.2 ×100
% Error = 0.1105 ×100
% Error = 11.05
Therefore the percentage error is 11.05%
 
        
             
        
        
        
 Best Answer:  <span>(a) 
8.9 x 10^-7 = x^2 / 0.15-x 
x = [OH-] = 0.00037 M 
pOH = 3.4 
pH = 14 - 3.4 = 10.6 
(b) 
Ka = Kw/Kb = 5.6 x 10^-10 = x^2 / 0.20-x 
x = [H+] = 0.000011 M 
pH = 5.0</span>
        
             
        
        
        
Answer: Iron gains electrons mean It is reduced
Explanation:
Oxidation-reduction reaction or redox reaction is defined as the reaction in which oxidation and reduction reactions occur simultaneously.
Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation state of the substance increases.

Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced.

Thus iron gains electrons mean It is reduced