Question

Sabendo as massas atômicas a seguir em g/mol: Ca - 40, O- 16, H-1, Al-27, Cl- 35,5. Assinale a alternativa que possui as massas molares das moléculas Ca(OH)2, Al(OH)3, H2O2, CaCl2, respectivamente:

a) 74, 78, 34, 111
b) 58, 45, 34, 75,5
c) 58, 45, 18, 75,5
d) 74, 78, 18, 111

Answer 1

a) 74, 78, 34, 111

$M_{Ca(OH)_2} = 40 + (16 + 1) \cdot 2 = 40 + 17 \cdot 2 = 40 + 34 = 74g/mol\\M_{Al(OH)_3} = 27 + (16 + 1) \cdot 3 = 27 + 17 \cdot 3 = 27 + 51 = 78g/mol\\M_{H_2O_2} = 1 \cdot 2 + 16 \cdot 2 = 2 + 32 = 34g/mol\\M_{CaCl_2} = 40 + 35,5 \cdot 2 = 40 + 71 = 111g/mol$