What is the molarity of a solution that contains 10.66g of sodium sulfate dissol

Question

What is the molarity of a solution that contains 10.66g of sodium sulfate dissolved in 250.0ml of solution? What is the mass of potassium dichromate present in 50.0mL. of a 0.105M solution? What volume of a 2.0M HCI solution must be diluted to produce 500.mL of a 0.125M HCl solution? What volume of a 0.225M HCI solution is required to neutralize (reactwith) 23.3g of Mg(OH)2? The balanced reaction is: 2 HCI(aq) + Mg(OH)2(s) 2 H2O() + MgCl2(aq) ead section 4.9, pages 159-165 before answering #s10 and 11 number of rach element in the following substances.

Explanation / Answer

1) Molarity = (W/MW) (1000 / v in mL)

W = 10.66 g

MW = 142.04 g /mol

V = 250 mL

Molarity = (10.66 / 142.04) (1000 / 250)

Molarity = 0.30 M

2) Molarity = (W/MW) (1000 / V in mL)

Molarity = 0.105 M

W = ?

V = 50.0 mL

MW = 294.185 g /mol

0.105 = (W / 294.185) (1000 / 50.0)

0.00525 = W / 294.185

W = 1.54 g

mass of dichromate required = 1.54 g

3) according to dilution law

M1V1 = M2V2

M1 = 2.0 M , V1 = ?

M2 = 0.125 M , V2 = 500 mL

V1 = (M2V2 / M1)

V1 = (0.125 x 500 / 2.0)

V1 = 31.25 mL

31.25 mL 2.0 M HCl must be diluted to 500mL

4) moles of Mg(OH)2 = 23.3 / 58.32 = 0.40

0.40 x 2 = 0.80 moles must be added to neutralize given base

M = n/V

V = n /M

V = 0.80 / 0.225

V = 3.55 L

3.55 L HCl required

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