Chlorine can evaporate but there is another enemy in there called Chloramine, it is harmful to plant cells and is also harmful to you. Keep in mind you will be smoking that plant(I assume). It can not be aerated out or evaporate. I would recommend filtering your water with a carbon based filter. I realize it is not always an option for everyone but I always recommend it. Aside form Chloramine, there is plenty of other crap in tap water you should be concerned about accumulating in the plant.
Do you have a meter to find out what TDS your tap water is running at? If you are under 150 PPM you should have no problem using the water as is. If you prefer to pH your water, I would always recommend using something more natural. Lemon Juice, non-filtered Apple Cider/juice, Grape juice, etc. The more sediment the better. Those little particles of fruit sediment act as pH buffering zones in the soil, they help stabilize the pH for fairly long periods of time. Depending on your choice it can even be more cost effective also. non-filtered Apple juice is more expensive than Grape juice, etc. Just depends on what you have access to.
Aside from the benefits of pH buffering, you also get various trace elements, some macro nutrients like potassium, secondaries like Calcium, magnesium, etc.