Deleting all related list when a record is deleted in lookup

I have a custom object let say as Merchant__c. I also created a lookup field in my Account object which is related to my Merchant__c object.Deleted to Account delete all related Merchant__c record.

trigger DeleteAllRelatedMerchant on Account (Before Delete) { 
set<ID> accountSet = new set<ID>(); 
for(Account a :trigger.old){
     accountSet.add(a.ID); 
}
 list<Merchant__c> merchantList = [SELECT Id,name from Merchant__c where Account__c IN:accountSet];
 delete merchantList; 
}