QUESTION 1 Magnesium chloride (MgCl 2 ) dissolves completely in water. What is t

Question

QUESTION 1

Magnesium chloride (MgCl2) dissolves completely in water. What is the molarity of the Mg2+(aq) cation in a 0.00500 M MgCl2(aq) solution? (3 significant digits, units M)

1 points   

QUESTION 2

What is the molarity of Cl-(aq) anion in the same solution as Question 1? (3 significant digits, units M)

1 points   

QUESTION 3

The parts per million (ppm) unit can be expressed as mg solute per liter solution (mg/L) for dilute aqueous solutions. Convert the Mg2+(aq)concentration from Question 1 into units of ppm. Use the molecular weight of the ion in the conversion. (Round to 3 significant digits, units ppm)

1 points   

QUESTION 4

Convert the Cl-(aq) concentration from Question 2 into units of ppm. (Round to 3 significant digits, units ppm)

1 points   

QUESTION 5

How many grams of Mg2+(aq) are contained in 100.0 g of 0.00500 M MgCl2(aq) solution? Assume the solution density is 1.0 g/mL, like water. (Round to 3 significant digits, unit g)

1 points   

QUESTION 6

What is the % by mass of Mg2+(aq) in the solution from Question 5? (Round to 3 significant digits, unit %)

1 points   

QUESTION 7

Questions 7 through 10 are linked together. A solution of red dye #40 was made with a concentration of 0.000440 M. Use Beer's Law, A = ebcwhere c stands for the concentration, to calculate the absorbance (A) if the value of the molar absorptivity (e) is 1700 Lmol-1cm-1 and the cell length (b, the diameter of the vial) is 2 cm. (Use 4 significant digits, no units)

1 points   

QUESTION 8

A student diluted the original 0.000440 M red dye solution (from Question 7) by measuring 25.00 mL with a pipet into a 100.0 mL volumetric flask and then adding water up to the line on the flask. Calculate the new concentration of the diluted solution. (Round to 3 significant digits, unit M)

1 points   

QUESTION 9

The absorbance was 0.388 when the student's diluted solution (from Question 8) was measured in the Microlab spectrometer. Use the e and b values from Question 7 to calculate the actual concentration of the diluted solution. (Round to 3 significant digits, unit M)

1 points   

QUESTION 10

The student desires a concentration of 0.000044 M, exactly one tenth of the original red dye solution strength. What volume of the original 0.000440 M solution should be measured into a 100.0 volumetric flask, to be diluted with water up to the line of the flask? (3 significant digits, unit mL)

Explanation / Answer

Question 1:

ans:Given that molarity of MgCl2 solution is 0.00500M

It can dissociate sinto Mg2+ and 2Cl-

so the concentration of Mg2+ ion is 0.00500M

Question 2:

Ans:The concentration of Cl- ion is twice the concentration of MgCl2

so the concentration of Cl- is 2*0.00500=0.010M

Question 3:

0.12g=10.00mg

Question 4:

350.0mg

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