Which of the following isotopes is not commonly used for dating objects? a. carbon-14 b. phosphorus-32 c. potassium-40 d. rubidium-87

The correct answer is phosphorus-32-32.

Explanation:

Phosphorus-32 is an isotope of phosphorus found in many organic molecules. They are used to detect metabolic pathways of involving bio-molecules. Also used to detect malignant tumors in the body of the living being.

Where as:

Carbon-14 is used for carbon-14 dating also known as radiocarbon dating. this is used to determine age of  old objects.

Potassium-40 id used to determination of age of rocks and minerals. Specially used in potassium argon dating.

Rubidium-87 is an isotope of rubidium element used to  determine age of rocks.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%