## Units

$E=hv$

Jaedyn_Birchmier3F
Posts: 30
Joined: Fri Sep 28, 2018 12:26 am

### Units

I'm a little confused on how the units cancel out for the equation E= hv. Planck's constant is represented in J x s while frequency is represented in Hertz. How does the multiplication of Hertz with Joules and seconds end up canceling out to just have E in units of Joules?

Ashley Zhu 1A
Posts: 69
Joined: Fri Sep 28, 2018 12:16 am

### Re: Units

The unit "hertz" means 1/seconds, so when you multiply J x s by Hz = 1/s, the seconds cancel out and you're left with J.

tierra parker 1J
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

### Re: Units

hertz is equivalent to per second (1 s^-1) so in the equation E=hv, h has units of J x s and v has units of 1/s so when you multiply the two cancel out to get J which is the unit for energy

Posts: 30
Joined: Fri Sep 28, 2018 12:24 am

### Re: Units

Frequency is represented by Hz (or 1/s) when doing the calculations the h units cancel with the seconds and J is left. Which shows the units for energy is J, as said before in the other replies.

Nicolle Fernandez 1E
Posts: 56
Joined: Fri Sep 28, 2018 12:25 am
Been upvoted: 1 time

### Re: Units

Since hertz is 1/second when you multiply (J x second)(1/second) the seconds cancel out which leads to J.

Minsub Lee 3E
Posts: 32
Joined: Fri Sep 28, 2018 12:25 am

### Re: Units

I like to write it out like in dimensional analysis. It will help you follow your work, and you can clearly see what can be cancelled out. Since 1 Hertz is 1/s, if you multiply it with Jxs, the s will be cancelled out, leaving just s. I suggest writing out the units in your work for dimensional analysis throughout chemistry problems such as converting moles to grams and comparing molar ratios.