Question

question 3 (1 point)
for a 25.0 % m/v mgcl₂ solution, what is the molarity ? in problem 2 we determined
that this is a 2.63 m solution.
first we have to convert moles into equivalents
mgcl₂ → mg⁺² + 2 cl⁻¹
1 mol = 1 equivalents
2 mol 3 eq
(----------)(-----------) = 4 eq/l
5 l 6 mol
a. 250. b. 100.0 c. 2 d. 30.00 e. 6 f. 24
g. 3 h. 36 i. 18.0 j. 1 k. 6.00 × 10⁻³ l. 3.60 × 10⁻²
m. 6.00 × 10⁻³ n. 5 o. 3.0 × 10⁻² p. 1.80 × 10⁻²
q. 7.65 × 10⁻¹⁰ r. 2.63 s. 7.89 t. 5.26 u. 10¹²
v. 10⁹ w. 10⁶ x. 10³ y. 95.21 z. 10

Explanation:

Step1: Determine equivalents per mole

From the dissociation equation \(MgCl_{2}\to Mg^{2 +}+2Cl^{-}\), for \(MgCl_{2}\), the total charge per formula unit is \(2 + 2\times1=3\) (1 \(Mg^{2+}\) with charge \(+ 2\) and 2 \(Cl^{-}\) with charge \(-1\) each). But in terms of equivalents (where equivalent is based on the total positive or negative charge), for \(MgCl_{2}\), 1 mol of \(MgCl_{2}\) gives 3 equivalents (2 from \(Cl^{-}\) and 1 from \(Mg^{2+}\)). So \(1\space mol = 3\space equivalents\) (answer for blank 1 is G).

Step2: Fill in the molarity value

We know the molarity \(M=\frac{mol}{L}\) and from problem 2, \(M = 2.63\space M\). So the value for blank 2 is R (\(2.63\space mol\)).

Step3: Calculate equivalents

Using the conversion factor \(\frac{3\space eq}{1\space mol}\), if we have \(2.63\space mol\), then the number of equivalents is \(2.63\times3 = 7.89\space eq\) (answer for blank 3 is S).

Step4: Assume volume

Since molarity \(M=\frac{mol}{L}\), and we are calculating normality \(N=\frac{eq}{L}\), if we consider the volume as \(1\space L\) (because molarity is given as moles per liter and we use the same volume for normality calculation). So blank 5 is \(1\space L\) (but looking at the options, if we assume the formula \(N = M\times n\) (where \(n\) is the number of equivalents per mole), and \(M = 2.63\space M\), \(n = 3\)). The formula \((\frac{2.63\space mol}{1\space L})\times(\frac{3\space eq}{1\space mol})=7.89\space eq/L\). So blank 4 is S (\(7.89\space eq/L\)).

Answer:

1. G. 3
2. R. 2.63
3. S. 7.89
4. S. 7.89
5. (Assuming volume as \(1\space L\) which is not in the options, but based on the formula \(N = M\times n\) with \(M = 2.63\) and \(n = 3\) the result for the calculation part gives 7.89 for blank 4)