=calculez masa si moli de acid din solutie
c=mdx100/ms---> md= 438x25/100g= 109,5g
niu=m/M= 109,5g/36,5 g/mol= 3molHCL
=calculez moli de Ca, sare si H2 din ecuatia chimica
1mol.....2mol......1mol..........1mol
Ca + 2HCl---> CaCL2 + H2
x.............3..............y..................z
x= 1,5mol Ca----> m= niuxM= 1,5molx40g/mol= 60gCa
y= 1,5mol CaCl2
z= 1,5mol H2