Question

1. What is the concentration of K+ in 0.15 M of K2S?

Express your answer to one decimal place and include the appropriate units.

2.A scientist wants to make a solution of tribasic sodium phosphate, Na3PO4, for a laboratory experiment. How many grams of Na3PO4will be needed to produce 525 mL of a solution that has a concentration of Na+ ions of 1.50 M ?

Express your answer to three significant figures and include the appropriate units.

3.Part A - Using Molarity to Calculate Grams of Solute

What is the concentration of ammonia in a solution made by dissolving 3.75 g of ammonia in 120.0 L of water?

4.One cup of fresh orange juice contains 125 mg of ascorbic acid (vitamin C, C6H8O6). Given that one cup = 238.4 mL calculate the molarity of vitamin C in organic juice

5.How many milligrams of sodium sulfide are needed to completely react with 25.00 mL of a 0.0100 M aqueous solution of cadmium nitrate, to form a precipitate of CdS(s)?

6. Part A - Determining the Quantity of Solute by Titration

A mysterious white powder is found at a crime scene. A simple chemical analysis concludes that the powder is a mixture of sugar and morphine (C17H19NO3), a weak base similar to ammonia. The crime lab takes 10.00 mg of the mysterious white powder, dissolves it in 100.00 mL water, and titrates it to the equivalence point with 2.84 mL of a standard 0.0100 M  HCl solution. What is the percentage of morphine in the white powder?.

7. Of the species below, only ________ is not an electrolyte.

LiNO3

RbOH

HI

NaBr

Kr

8.Of the species below, only ________ is not an electrolyte..

	Ar
	Rb2SO4
	HCl
	KOH
	NaCl

Answer 1

1.
K2S ---> 2K+ + S2-
So,
concentartion of K+ = 2* concentration of K2S
                                        = 2*0.15
                                         =0.3 M

2.
[Na3PO4] = [Na+]/3
                     =1.5/3
                     =0.5 M
V= 525 mL = 0.525 L
Number of moles of Na3PO4 = M*V = 0.5*0.525 = 0.2625 mol
Molar mass of Na3PO4 = 164 g/mol
mass of Na3PO4 = number of moles * molar mass
                                  = 0.2625 * 164
                                   = 43.05 g
Answer: 43.05

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