Element X reacts with Sodium to form the ionic compound Na2X.  What is element X if its anion has 18 electrons? A. S B. Ar C. Se D. Br    

What is the oxidation state of manganese in MnO4-? A.  +1 B.  +3 C.  +5 D.  +7

What is the mass of 0.1000 mole of AlCl3

The pH of a 0.25 M aqueous solution of acetic acid, CH3CO2H, is 2.67 at 25

What is the hydroxide ion concentration, , in a solution with a pH of 8.472 at 25

The equilibrium constant, K, is 2.4 x 103 at a certain temperature for the reaction: 2NO(g) ⇌ N2(g) + O2(g) For which of the following sets of conditions is the system at equilibrium? A.  1.0-L flask contains 0.024 mol NO, 2.0 mol N2, and 2.6 mol O2. B.  2.0-L flask contains 0.032 mol NO, 0.62 mol N2, and 4.0 mol O2. C.  3.0-L flask contains 0.060 mol NO, 2.4 mol N2, and 1.7 mol O2. D. None of these conditions are at equilibrium  

What is the molar concentration of a solution formed by dissolving 300.0 mg of Glucose, C6H12O6, to make 150.0 mL of solution? Molar mass:C6H12O6: 180.18 g/mol   A. 0.360 M B. 11.1 M C. 1.67 x 10-3 M D. 1.11 x 10-2 M

Which ion has the smallest radius? A. Cl- B. S2- C. Mg2+ D. Na+  

What volume of a 1.25 M aqueous solution of sodium chloride is needed to prepare 100.0 mL of a solution that is 0.25 M? A. 16.0 mL B. 20.0 mL C. 50.0 mL D. 80.0 mL

Which statements are true? I. Atoms with both a sigma- and pi-bond between them are stronger than atoms with only a sigma-bond between them. II. A molecule that is sp hybridized has a trigonal planar geometry III. Rotation is restricted between two atoms containing both sigma and pi bonds between them. IV. The molecule CH4 contains both sigma and pi bonds between the Carbon and Hydrogen   A. I, II, and III B. II and IV C. I and III D. All are correct