missed this day of class! Help please What is the molarity of a solution made by

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missed this day of class! Help please

What is the molarity of a solution made by dissolving 5.00 grams of Ca(NO3)2 in enough water to make 75.0 mL of solution? Report your answer to three places past the decimal point. ____________ M 2. What mass of KCl is required to make 41 ml of a 0.11 M KCl solution? Report your answer to three places past the decimal point. _________ g KCl What mass of Al2(SO4)3 is required to make 58 mL of a 0.035-M solution of Al2(SO4)3? _________ g How many moles of sulfate ions are present in the solution? ________ mol 4. What is the total concentration of all ions (the sum of their individual concentrations) in aqueous solutions of the following salts? (Hint: Each substance is an electrolyte that dissociates in water to produce ions. Use a table of polyatomic ions if you do not recognize a polyatomic ion.) (a) 0.0789 M of CuSO4 _________ M (b) 0.0597 M of Na3PO4 _______ M (c) 0.0647 M of CaCl2 ____________ M

Explanation / Answer

1.

Molarity = Moles / Volume (in L)

Mass = 5.00 g

Volume = 75.0 mL = 0.075 L

Molar mass = 164.088 g/mol

Moles = Mass / Molar mass

Moles = 5.00 / 164.088 = 0.03047 mol

Molarity = 0.03047 / 0.075 L

Molarity = 0.406 M

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2.

Molarity = 0.11 M

Volume = 41 mL = 0.041 L

Molarity = Moles / Volume(in L)

0.11 M = Moles / 0.041 L

Moles = 4.51 x 10^-3 mol

We know that, Moles = Mass / Molar mass

Mass = Moles x Molar mass

Mass = (4.51 x 10^-3 mol) x 74.55 g/mol (Molar mass of KCl = 74.55g/mol)

Mass = 0.3362 g

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3)

Molarity = 0.035 M

Volume = 58 mL = 0.058 L

Molarity = Moles / Volume(in L)

0.035 M = Moles / 0.058 L

Moles = 2.03 x 10^-3 mol

We know that, Moles = Mass / Molar mass

Mass = Moles x Molar mass

Mass = (2.03 x 10^-3 mol) x 342.15 g/mol (Molar mass of Al2(SO4)3 = 342.15)

Mass = 0.6945 g

Moles of Al2(SO4)3 = 2.03 x 10^-3 mol

Each mol of Al2(SO4)3 contains 3 mol of SO4^2- ions.

So, 2.03 x 10^-3 mol contains 3 x 2.03 x 10^-3 mol = 6.1 x 10^-3 mol

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4.

a)

0.0789 M CuSO4

1 M of CusO4 has one M Cu^2+ and one M SO4^2-

0.0789 M of CuSO4 has 0.0789 M Cu^2+ and 0.0789 M SO4^2- ion

Total = 1.578 M ions

b)

0.0597 M Na3PO4

1 M of Na3PO4 has 3M Na^+ and 1M PO4^3-

So, 0.0597 M Na3PO4 has 0.179M Na^+ and 0.0597 M PO4^3-

Total = 0.2388 M ions

c)

0.0647 M CaCl2

1 M of CaCl2 contains 1M Ca^2+ and 2M Cl^1- ions

0.0647 M CaCl2 contains 0.0647 M Ca^2+ and 0.1294M Cl^1- ions.

Total = 0.1941 M ions.

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