The what of an element is the average mass of all isotopes of that element

Given the balanced equation: 3fe3 + (aq) + al (s) → 3fe2 + (aq) + al3 + (aq) what is the total number of moles of electrons lost by 2 moles of al (s) ?

The volume of water that must be added in order to dilute 40mL of 9.0M HCl to a concentration of 6.0 M is closest to: (A) 10 mL (B) 20 mL (C) 30 mL (D) 40 mL (E) 60 mL

1. How many grams of nitrogen gas are produced when 47.9 mol of ammonium dichromate are decomposed in the following unbalanced equation? (NH), Cr, O. / (aq) - Cr Og (aq) + H2O + N2 (9)

Identify like terms: 8ab and ab, - 2b and - b

A student states that ALL Substances that are uniform throughout are pure substances. Why is this false?

Which of the following transitions would release energy? n=2->n=3 n=1 - > n=3 n=3 - >n=1 n=3->n=2

Which animal group actually saw a drop in the number of endangered and threatened species between 1995 and 2005? a Fish b. Reptiles c. Birds d. Mammals

Why does burning fossil fuels put ecosystems under pressure?

What is the quantum number set of the ground-state electron that is found in helium (He) but not in hydrogen (H) ? (1, 0, 0, - ½) (1, 0, 1, - ½) (1, 1, 0, - ½) (1, 1, 1, - ½)

What must be true in order for magnetism to induce an electric current in a wire? There needs to be a switch in the circuit. There cannot be a switch in the circuit. The wire must be part of a closed circuit. The wire must be part of an open circuit.