You are blocking all traffic from that network to the IT network. Ping is an application that uses ICMP echo requests and echo replies. but you are blocking the replies. If you want to block the requests, but not the replies, then you need to use an extended access list that does that.
permit icmp 192.168.10.0.0 0.0.0.31 172.16.0.0 0.0.0.15 echo-reply
Standard access lists are placed outbound as close to the destination as possible so as to not block too much traffic, but extended access lists should be placed inbound as close to the source as possible so as to not route traffic that is destined to be dropped. You can do that with extended access lists because they have both the source and destination, while standard access lists do not.
Also, notice that your wildcard masks are wrong for the mask length in the diagram, and the diagram does not have a Router 3 as your question says.