The items are answered below and are numbered separately for each compound.
The freezing point of impure solution is calculated through the equation,
Tf = Tfw - (Kf)(m)
where Tf is the freezing point, Tfw is the freezing point of water, Kf is the freezing point constant and m is the molality. For water, Kf is equal to 1.86°C/m. In this regard, it is assumed that m as the unit of 0.25 is molarity.
1. NH4NO3
Tf = 0°C - (1.86°C/m)(0.25 M)(2) = -0.93°C
2. NiCl3
Tf = 0°C - (1.86°C/m)(0.25 M)(4) = -1.86°C
3. Al2(SO4)3
Tf = 0°C - (1.86 °C/m)(0.25 M)(5) = -2.325°C
For boiling points,
Tb = Tbw + (Kb)(m)
For water, Kb is equal to 0.51°C/m.
1. NH4NO3
Tb = 100°C + (0.51°C/m)(0.25 M)(2) = 100.255°C
2. NiCl3
Tb = 100°C + (0.51°C/m)(0.25 M)(4) = 100.51°C
3. Al2(SO4)3
Tb = 100°C + (0.51°C/m)(0.25 M)(5) = 100.6375°C
Answer:
-1.78 V
Explanation:
There are several rules required to calculate the cell potential:
- given standard cell potential, we may reverse the equation: the products of a given reaction become our reactants, while reactants become our products in the reversed equation. For a reversed equation, we change the sign of the cell potential to the opposite sign;
- if we multiply the whole equation by some number, this doesn't influence the cell potential value. It only produces a different expression in the equilibrium constant.
That said, notice that the initial reaction with respect to the final reaction is:
- reversed: chromium(III) cation and chloride anion become our reactants as opposed to the products in the initial reaction, so we change the sign of the cell potential to a negative value of -1.78 V;
- each coefficient is multiplied by a fraction of
. It doesn't influence the value of the cell potential.
Thus, we have a cell of E = -1.78 V.
Answer:
- <em>There are </em><u><em>4 moles</em></u><em> of chloride ions in 2 moles of calcium chloride.</em>
Explanation:
Start by writing the chemical formula of calcium chloride.
The suffix -ide in chloride means that chlorine is working as the ion Cl⁻, this is with oxidation state -1.
Calcium, being an alkaline earth metal, uses oxidation state +2, Ca²⁺
Then, two atoms of Cl are combined with one atom of calcium, because in this way each Cl atom will accept one electron from a Ca atom, which will donate its two valence electrons.
That is indicated in the chemical formula with subscripts: <u><em>CaCl₂</em></u>, meaning that each formula-unit of calcium chloride has 2 ions of chlorine and 1 ions of calcium, or twice the number of moles of chloride ion.
- 1 mol CaCl₂ : 1 mol Ca⁺ : 2 mol Cl⁻
⇒ 2 mol CaCl₂ : 2 mol Ca⁺ : 4 mol Cl⁻
Hence, there are 4 moles of chloride ions in 2 moles of calcium chloride.
Based on bond type, CaCI2 has the highest melting point.
