N=6.98*10²⁴
Nₐ=6.022*10²³ mol⁻¹
n(Mg)=N/Nₐ
m(Mg)=n(Mg)M(Mg)=M(Mg)N/Nₐ
m(Mg)=24.3g/mol*6.98*10²⁴/(6.022*10²³mol⁻¹)=281.7 g
        
             
        
        
        
Concentration of unknown acid is 0.061 M
Given:
Concentration of NaOH = 0.125 M
Volume of NaOH = 24.68 mL
Volume of acid solution = 50.00 mL
To Find:
Concentration of the unknown acid
Solution: Concentration is the abundance of a constituent divided by the total volume of a mixture. The concentration of the solution tells you how much solute has been dissolved in the solvent
Here we will use the formula for concentration:
 M1V1 = M2V2
 0.125 x 24.68 = 50 x M2
 M2 = 0.125 x 24.68 / 50
 M2 = 0.061 M
Hence, the concentration of unknown acid is 0.061 M
Learn more about Concentration here:
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Answer:
The correct answer is: Dynamic equilibrium in a chemical reaction is the condition in which the rate of the forward reaction equals the rate of the reverse reaction.
Explanation:
Dynamic equilibrium is a chemical equilibrium between froward reaction and backward or reverse reaction where rate of reaction going forwards is equal to the rate of reaction going backward (reverse).  
Some other properties of dynamic equilibrium are:
- Chemical equilibrium are attained is closed system.
- The macroscopic remains constant like: volume, pressure, energy etc.
- The concentration of the reactants and products remain constant.They are not always equal.
 
        
             
        
        
        
Answer:
400cal
Explanation:
Since ice melted at 0 Celesius then the heat gained by ice (latent heat) will melt it so you should substitute in that law
Q=mlf ..where Q is the heat required to convert ice to water , m is the mass of ice and lf is the latent heat of fusion
Q=5∗80=400cal
 
        
             
        
        
        
Zeff = Z - S
Here, Z is the number of protons in the nucleus, that is, atomic number, and S is the number of nonvalence electrons. 
For boron, the electronic configuration is 1s₂ 2s₂ 2p₄
Z = 5, S = 2 
Zeff = 5-2 = +3
For O, electronic configuration is 1s₂ 2s₂ 2p₄
Z = 8, S = 2
Zeff = 8-2 = +6
Hence, the correct answer is second option, that is, +3 and +6, the Zeff of boron is smaller in comparison to O, thus, boron exhibits a bigger size than O.