pgrep command can be used to find process id by the name of the process.

Example:
Lets find the process id of chrome

$ pgrep -li chrome
1155 Google Chrome
1162 Google Chrome H
1171 Google Chrome H
1172 Google Chrome H
1173 Google Chrome H
1174 Google Chrome H
1214 Google Chrome H
1271 Google Chrome H
1275 Google Chrome H