Which one of the following substances is

LEAST soluble in water?
1. BaCO3
2. KSCN
3. Na3PO4
4. RbOH
5. LiBr

1.BaCO3

To determine which substance is the least soluble in water among the given options, we need to consider the solubility rules.

1. BaCO3 (Barium carbonate): It is generally considered insoluble in water, so it has low solubility.
2. KSCN (Potassium thiocyanate): It is soluble in water, so it has high solubility.
3. Na3PO4 (Sodium phosphate): It is soluble in water, so it has high solubility.
4. RbOH (Rubidium hydroxide): It is soluble in water, so it has high solubility.
5. LiBr (Lithium bromide): It is soluble in water, so it has high solubility.

Based on the information given, the substance with the least solubility in water is BaCO3 (Barium carbonate), option 1.

To determine which substance is the least soluble in water, we need to compare the solubility of each substance. Solubility refers to the ability of a substance to dissolve in a particular solvent, in this case, water.

One way to determine the solubility is by consulting a solubility table or looking up the solubility of the substances in a reputable reference source. For this question, I will provide you with the solubility information.

Let's compare the solubility of each substance:

1. BaCO3 (Barium carbonate): Barium carbonate is sparingly soluble in water, meaning it has low solubility.
2. KSCN (Potassium thiocyanate): Potassium thiocyanate is highly soluble in water.
3. Na3PO4 (Sodium phosphate): Sodium phosphate is highly soluble in water.
4. RbOH (Rubidium hydroxide): Rubidium hydroxide is highly soluble in water.
5. LiBr (Lithium bromide): Lithium bromide is highly soluble in water.

Based on the provided solubility information, we can conclude that BaCO3 (Barium carbonate) is the least soluble in water among the given substances.

Remember, if you encounter similar questions in the future, you can consult a solubility table or reliable reference sources to find the solubility of substances in water.

See solubility rules.