I’m trying to export my vocals from the start to the end of the track,with all the empty space in front.im sending the track and vocals out to be mixed and mastered professionally,and the engineer is asking for my vocals separate and with the empty space before the vocals,so they sync with the track perfectly. Every time i export my vocals,there is no empty space,just a few seconds,then my first vocals start. thanks in advance for anyone that can help. 
Which Audacity version are you using? I thought we got rid of that problem in a recent version.
One way around this is to create a dead silent track (Generate > Silence) the length of the whole show. When you File > Export Selection, select the silent track along with the desired track. Audacity will smash both tracks together on export. Since the silent track was there from the beginning, it will fill in the gaps.
Click just above the MUTE button to select a whole track. Shift-Click to get two or more.
Koz
No, it’s harder now to export with leading white space, given Tracks > Mix and Render no longer converts that leading space to silence.
Gale