Using SOQL queries in REST API request - Salesforce

Hi everybody,

I am trying to fetch Accounts from another salesforce org by using a httprequest instance. I have obtained the security token from the other org , my code extract for the query is as follows:

{httprequest req = new httprequest();
http testHttp = new http();

req.setMethod('GET');
req.setEndPoint('https://ap2.salesforce.com/services/data/v38.0/query/?q=SELECT id,Name FROM Account');
req.setHeader('Authorization','OAuth *Here is the token*');
HttpResponse res = testHttp.send(req); }

But it is giving me Error Code: 400

Any suggestions?? Thanks