a) n HNO3 = 0.60 mol
0.60 = \frac{m}{1.008+14.01+16.00(3)}
m = 0.60 x 63.018
For HNO3 the mass you should be 38g (2 sig figs)
b) n Mg(NO3)2 = 0.30 mol
m = 0.30 x molar mass
= 44g (2 sig figs)
Really depends. But the criteria for medical admission for most unis are based on 1/3 ATAR, 1/3 UMAT and 1/3 Interview. That being said, most unis give out interview offers based on your atar and umat scores. So i'll say that umat and atar are both important, so don't stuff up in either.
hmm not sure whats wrong with ur keyboard, but it's spelt medicine.
As to O.P. If you have a certain interest, you should take the umat, and work hard as med is very competitive.
Pretty stupid to be asking these types of questions now. UMAT is coming up around 2 months time and u don't even know wtf it is.
P.S. Go register for umat