Pre-lab LO1 ater Hardness (10pts) Name Date Please review the background knowled

Question

Pre-lab LO1 ater Hardness (10pts) Name Date Please review the background knowledge posted on icollege. Answer the following questions. 1. Hardness is defined as calcium and magnesium ion content. Since most hardness is caused by carbonate mineral deposits and does not distinguish calcium and magnesium ions, hardness is usually reported as parts per million ppm of calcium carbonate (CaCO2, by weight). A water supply with a hardness of 100 ppm contains the equivalent of 100 g of CaCO3 in 1 million g of water or 0.1 g in 1 L of water (or 1000 g of water since the density of water is about 1 g/mL). For a water supply with a hardness 134 ppm. what is its hardness in mol L? Show your work 2. 0.405 g of CaCO3 is dissolved in HCl and diluted to a volume of 250.00 mL. What is the molarity of calcium ions in the solution? You can use the following steps to solve the problem a. Determine the molar mass of CaCO b. Determine the mole of 0.405 g of CaCO3 c. Determine the solution volume in Liter d. Use the mole of the solute (Ca2t) and the volume of the solution to determine the molarity of calcium ions

Explanation / Answer

1] 1ppm = 1mg/L

134 ppm = 134 mg/L

134*10^-3 / 100 = 1.34*10^-3 mol/L

2]

CaCO3 = 40+12+48 = 100 gms

Moles = mass/MW = 4.05*10^-3

V = 0.25L

Molarity = Moles / Volume in L =  4.05*10^-3 / 0.25 = 0.0162 M

CaCO3 --->Ca+2 +CO3-2

[Ca+2] = 0.0162 M

3]

M1V1 = M2V1

25*0.0162 = 27.25*M2

M2 = 0.01486 M ---Molarity of EDTA

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