my newly acquired mandarin tree is losing all of its leaves, is this normal?
Not really but citrus trees are a bit fussy and sometimes drop leaves when they have a bit of a shock such as when being repotted or moved. They also don't like being over-watered so don't water until the top of the compost is dry. Once settled in they normally regrow any lost leaves. Some good tips here:
thank you all for your valuable answers speak to you all soon, happy gardening.