Consider this ion, PO33–. How many valence electrons must be included  its Lewis structure?

Which gas, krypton or argon, diffuses faster under the same conditions?

Calculate the energy of a photon with a wavelength of 535 nm.   h = 6.626×-34 J∙s and c = 2.998×108 m∙s–1

How many moles  of Al2O3 can be  produced from the reaction of 81 g Al with 2.0 mol Fe2O3? 2Al + Fe2O3 –> Al2O3 + 2Fe  

 20.0 L of NH3 gas at 1.05 atm and 22 oC is allowed to passed through 250. mL of 1.20 M HCl until the reaction is complete. What amount, in moles, of NH4Cl can be formed? NH3 (g) + HCl (aq) –> NH4Cl (aq)

Which sample represents a larger mass?

In the structure below octet rule is fulfilled for al atoms but lone electron pairs are not shown. Determine the molecular geometry around the N atom in this molecule.

Carbon tetrachloride, CCl4,  is a liquid with the density of 1.59 g/mL and molar mass of 153.8 g.  How many moles are present in a 10.0 mL sample of CCl4?

When a 45.0 g sample of a certain metal at 100.0 °C is dropped into a coffee cup calorimeter containing 100.0 g of water at 25.0 °C, the thermal equilibrium is reached at 37.0 °C.  What is the specific heat of the metal?  The specific heat of H2O(l) is 4.184 J·g–1·°C–1. Assume no heat is lost to the walls of the cup and to the surroundings.

Which of the following is mismatched: