No need to be exact. Just estimate the amount based on the container weight and amount. In other words, figure out the percentage and guestimate from there.
Calcium chloride won't chemically raise the ph. However, I have seen some ph rise in some cases, which I suspect might be due to carbon dioxide offgassing as the chemical is added. Possibly due to the creation of nucleation sites, which is how the coke and mentos reaction happens. Note that this is just speculation.