So what we know:
-Atomic Mass = Protons + Neutrons
-Atomic Number is the number of protons
Magnesium's atomic number is 12, so the natural occurring isotope for magnesium is Mg-12 (12 protons and 12 neutrons). Added up we have an atomic mass of 24 amu. Which means if we added one neutron in Mg-13, our atomic mass would be 25 amu.
We can use the equation:
(amu of isotope 1)x + (amu of isotop 2)(x-1) = Average atomic mass
where isotope 1 is the fractional abundance we're solving for.
Plugged in it looks like this:
24x + 25(1-x) = 24.3
Now to solve for x:
24x + 25 - 25x = 24.3
-x + 25 = 24.3
-x = -.7
x = .7
So in this case, the fractional abundance of Mg-12 would be .7, or 70%.<span />
Answer:
a. in pure water Solubility (x) = 1.26 x 10⁻⁴M
b. in 0.202M M⁺² Solubility (x) = 9.963 x 10⁻¹²M
The large drop in solubility is consistent with the common ion effect.
Explanation:
a. Solubility in pure water
Given: M(OH)₂ ⇄ M⁺² + 2OH⁻
I --- 0 0
C --- x 2x
E --- x 2x
Ksp = [M⁺²][OH⁻]² = (x)(2x)² = 4x³ => x = CubeRt(Ksp/4)
solubility in pure water = x = CubeRt(8.05 x 10⁻¹²/4) = 1.26 x 10⁻⁴M
b. Solubility in presence of 0.202M M⁺² as common ion.
Given: M(OH)₂ ⇄ M⁺² + 2OH⁻
I --- 0.202M 0
C --- +x +2x
E --- 0.202M + x 2x
≈ 0.202M
Ksp = [M⁺²][2x]² = (0.202)(2x)² = (0.202)(4x²) = 8.05 x 10⁻¹²
=> x = (8.05 x 10⁻¹²)/(0.202)(4) = 9.963 x 10⁻¹²M
The answer should be D. A rate law needs to be rate equaling the rate constant which is represented as k (make sure you use a lower case k since an upper case K is for equilibrium) times the concentrations of each reactant raised to the power of what ever order it has. (if A was a zero order it would be [A]⁰ and if A was third order it would be [A]³).
Do not get the order the reactants are confused with the coefficients in the chemical equation. (just because the reaction has 2B does not mean the rate law will have [B]². As shown in this example since it is first order therefore being [B] in the rate law)
I hope this helps. Let me know if anything is unclear in the comments.
Do you need help with all 3 questions or just the one that’s unanswered?
Metallic bonds are found in metals like zinc.
