For water hardness experiment using EDTA titrant:

1. Suppose water hardness was 600mg CaCO3/L, how much sample should be used to ensure 10-50mL of titrant will be used (assuming titer of 1.00mg CaCO3/ml EDTA)

2. How can EDTA be used to analyze other multivalent cations? If not, why?

You want to use about 40 mL of the titrant which is 1 mg/mL. That means

1 mg/mL x 40 mL = about 40 mg sample.
To get 40 mg of the sample, which is 600 mg/L (600 mg/1000 mL = 0.600 mg/mL) means
0.600 mg/mL x ?mL = 40 mg and solve for mL. I get about 66.7 mL. That isn't conveniently measured so I would take a 50 mL aliquot. Work that through to make sure you use between 10 and 50 mL but I think that will be 30 mL of the titrant. Check that out.

2. Yes, EDTA can be used to analyze other cations so I don't understand the if not, why part.

To solve the water hardness experiment using EDTA as the titrant, we need to calculate the amount of sample that should be used in order to ensure the desired volume range of titrant.

1. Calculation for Sample Size:
Water hardness is usually expressed in terms of milligrams of calcium carbonate (CaCO3) per liter (mg CaCO3/L). In this case, the water hardness is 600mg CaCO3/L.

The titer of the EDTA solution is given as 1.00mg CaCO3/ml. This means that 1 mL of EDTA solution is required to react with 1.00 mg of CaCO3.

To calculate the required sample size:
Total amount of CaCO3 in the sample = Water hardness × Sample Volume

We need to ensure that 10-50 mL of the titrant is used. So let's calculate the required sample size for both ends of the volume range:

For 10 mL of the titrant:
Sample size = (Water hardness × Sample Volume) / titer
= (600 mg CaCO3/L × 10 mL) / (1.00 mg CaCO3/mL)
= 6000 mg CaCO3

For 50 mL of the titrant:
Sample size = (Water hardness × Sample Volume) / titer
= (600 mg CaCO3/L × 50 mL) / (1.00 mg CaCO3/mL)
= 30,000 mg CaCO3

Therefore, to ensure 10-50 mL of the titrant will be used, you will need to use a sample size ranging from 6000 mg CaCO3 to 30,000 mg CaCO3.

2. EDTA can be used to analyze other multivalent cations because it forms stable complexes with these cations, similar to its reaction with calcium ions. The EDTA molecule contains multiple amine groups that can bind to metal ions, making it a versatile chelating agent.

However, EDTA has selectivity towards certain cations. It has a higher affinity for calcium and magnesium ions compared to other multivalent cations. This selectivity can be altered by adjusting the pH of the solution or using masking agents to prevent interference from other cations.

Nevertheless, the use of EDTA for other multivalent cations depends on factors such as the stability constant of the metal-EDTA complex and the presence of interfering ions. It may require specific modifications in the analytical procedure to ensure accurate analysis of these cations.