Rare earth metals are a group of 17 elements - lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium - that appear in low concentrations in the ground
Answer:
Explanation:
a).
conc of Ca²⁺ =0.0025 M
pCa = -log(0.0025) = 2.6
logK,= 10.65 So lc = 4.47 x 10.
Formation constant of Ca(EDTA)]-z= 4.47 x 10¹⁰ At pH = 11, the fraction of EDTA that exists Y⁻⁴ is 
=0.81
So the Conditional Formation constant= 
=0.81x 4.47 x10¹⁰
=3.62x10¹⁰
b)
At Equivalence point:
Ca²⁺ forms 1:1 complex with EDTA At equivalence point,
Number of moles of Ca²⁺= Number of moles of EDTA Number of moles of Ca²⁺ = M×V = 0.00250 M × 50.00 mL = 0.125 mol
Number of moles of EDTA= 0.125 mol
Volume of EDTA required = moles/Molarity = 0.125 mol / 0.0050 M = 25.00 mL
V e= 25.00 mL
At equivalence point, all Ca²⁺ is converted to [CaY²⁻] complex. So the concentration of Ca²⁺ is determined by the dissociation of [CaY²⁻] complex.
![[CaY^{2-}] = \frac{Initial,moles,of, Ca^{2+}}{Total,Volume} = \frac{0.125mol}{(50.00+25.00)mL} = 0.001667M](https://tex.z-dn.net/?f=%5BCaY%5E%7B2-%7D%5D%20%3D%20%5Cfrac%7BInitial%2Cmoles%2Cof%2C%20Ca%5E%7B2%2B%7D%7D%7BTotal%2CVolume%7D%20%3D%20%5Cfrac%7B0.125mol%7D%7B%2850.00%2B25.00%29mL%7D%20%3D%200.001667M)
Ca²⁺ + Y⁴ ⇄ CaY²⁻
Initial 0 0 0.001667
change +x +x -x
equilibrium x x 0.001667 - x
![{K^'}_f = \frac{[CaY^{2-}]}{[Ca^{2+}][Y^4]}=\frac{0.001667-x}{x.x} =\frac{0.001667-x}{x^2}\\\\x^2 = \frac{0.001667-x}{{K^'}_f}\\ \\](https://tex.z-dn.net/?f=%7BK%5E%27%7D_f%20%3D%20%5Cfrac%7B%5BCaY%5E%7B2-%7D%5D%7D%7B%5BCa%5E%7B2%2B%7D%5D%5BY%5E4%5D%7D%3D%5Cfrac%7B0.001667-x%7D%7Bx.x%7D%20%3D%5Cfrac%7B0.001667-x%7D%7Bx%5E2%7D%5C%5C%5C%5Cx%5E2%20%3D%20%5Cfrac%7B0.001667-x%7D%7B%7BK%5E%27%7D_f%7D%5C%5C%20%5C%5C)
x = 2.15×10⁻⁷
[Ca+2] = 2.15x10⁻⁷ M
pca = —log(2 15x101= 6.7
Answer:
(a). 5.4 × 10^23 atoms.
(b). 0.8928 moles Ni.
Explanation:
The first thing to do is to convert surface area from the in^2 to cm^2 and also the thickness unit to cm.
Therefore, 200 in^2 = 1290.3 cm^2 and 0.002 in = 0.00508 cm.
The next thing to do is to calculate the volume by using the formula below;
Volume= A × d. Where A = area and d = thickness.
Then, volume = 1290.3 × 0.00508= 6.55 cm^3.
Although not given but the Density if Nickel = 8 g/cm^3.
We know that the formula for Calculating density = mass / volume. So, we have ; mass = density × volume.
Mass= 8 × 6.55 = 52.4 g.
(a). The number of atoms of Nickel= moles × Avogrado's number.
Numbers of moles= mass / molar mass.
==> 52.4 / 58.6934 = 0.8928 moles.
Then, the number of atoms of Nickel = 0.8928 × 6.02 × 10^23.
= 5.4 × 10^23 atoms.
(b). The number of moles of Nickel has been Calculated in (a) above to be = 0.8928 moles Ni.
The answer is d noble gas because the very last column on the periodic table is all the noble gases
the states of the reactants and products
the temperature and pressure at which the reaction was carried out
the relative amounts of reactants and products
the type of catalyst that is used to speed up the reaction
whether the reaction can go in both directions
Explanation:
A chemical equation is an equation that shows how the reactants are combining together to give the products.
The following are the information to include when writing a chemical equation;
- the states of the reactants and products
whether solid, liquid or gases or aqueous, It is usually appended as a subscript in bracket
- the temperature and pressure at which the reaction was carried out
this shows the condition under which the reaction was carried out. It also gives useful information that can be used to quantitatively determine heat changes in a reaction.
- the relative amounts of reactants and products
this is usually derived from the balanced equation. They are the numbers appended at the beginning of the species in the equation
- the type of catalyst that is used to speed up the reaction
it is a good practices to provide the information about the catalyst used.
- whether the reaction can go in both directions
→ signifies one direction
⇔ both directions
learn more:
Chemical equation brainly.com/question/2924195
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