A laser emits light that has a frequency of 6.69 x 1014 s-1. If the laser emits a "pulse" (a burst of light) that contains 7.0 x 1017 photons, what is the total energy of that pulse in Joules? Do not use scientific notation in your answer. Give the answer ( in Joules) to 2 significant figures.

0.31 Joule

Explanation:

ΔE(per photon) = h·f = (6.63 x 10⁻³⁴J·s)(6.69 x 10¹⁴s⁻¹) = 4.44 x 10⁻¹⁹ J/photon X 7 x 10¹⁷photons = 0.31 Joules

consider the reaction below.

 no rx

at 500 k, the reaction is at equilibrium with the following concentrations.

[pci5]= 0.0095 m

[pci3] = 0.020

[ci2] = 0.020 m

what is the equilibrium constant for the given reaction?

0.042

0.42

2.4

24

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.