What element has 21 neutrons, 20 electrons and 20 protons

An ideal gas occupies a volume of 3.00 l at 2.70 atm and 27°c. if the temperature is raised to 33°c and the pressure is decreased to 1.20 atm, what is the final volume of the gas?

Why are mole ratios important to stoichiometry calculations?

Identify the oxidizing agent and the reducing agent in the reaction. 8H + (aq) + Cr 2O 7 2 - (aq) + 3SO 3 2 - (aq) → 2Cr 3 + (aq) + 3SO 4 2 - (aq) + 4H 2O (l)

What is the particle that is labeled with a question mark (?) in the diagram?

A saline solution contains 1.1% NaCl by mass. How much NaCl is present in 96.3 g of this solution

Determine the molecular formula for the unknown if the molecular mass is 60.0 amu and the empirical formula is ch2o.

Draw the organic product of the following nucleophilic reaction

How does the energy of the activated complex compare with the energies of reactants and products? select one: a. it is lower than the energy of both reactants and products. b.

A student asked to convert measurements from liters to mililiters and from mililiters to liters. His answers are shown in bold in the choices shown below. On which choice did he make a mistake?

Donald is making a model of a nitrogen atom. The box for nitrogen in the periodic table is shown. To represent a neutral atom, which of these must Donald include in his model?