What is the energy of a photon associated with a light of a wavelength of 550 nm?

A sample 3.91 x 1025 atoms of tungsten (W), what would the mass of the sample be in kilograms (kg)?

Which of the following electron transitions would emit energy?   a. n=5 → n=3  b. n= 2 → n=4 c. n=3 → n=6

Which of the following gases have the greatest root mean square velocity/speed?

The reaction of solid silicon (Si) with gaseous oxygen can be used to produce silicon trioxide. How many grams of silicon trioxide are produced in the reaction when 4.25 g of silicon reacts with 3.75 g of oxygen gas?    2Si (s) + 3O2 (g)

If a system releases heat and the volume of the container increases what are the signs of q and w? 

What is the formal charge of nitrogen in nitrogen tetrachloride (NCl4+)? 

How many moles K3PO4 would be produced if 15 moles of KOH were used in the reaction? The balanced chemical equation is given below.                       3KOH  +  H3PO4 ⟶  K3PO4  +  3H2O  

A flask contains 15.8 mL of a 1.42 M aqueous solution of KMnO4. A student adds 100.0 mL of water to the flask. What is the concentration of KMnO4 in the flask after the addition of the water?

Which of the following is correct formula for hydroiodic acid?