Answer:
4.8 g H₂O
Step-by-step explanation:
To find the mass of water, you need to (1) convert grams B₂H₆ to moles B₂H₆ (via molar mass from periodic table), then (2) convert moles B₂H₆ to moles H₂O (via mole-to-mole ratio from reaction coefficients), and then (3) convert moles H₂O to grams H₂O (via molar mass from periodic table).
It is important to arrange the ratios/conversions in a way that allows for the cancellation of units (the desired unit should be in the numerator). The final answer should have 2 sig figs because the given value (3.7 grams) has 2 sig figs.
Molar Mass (B₂H₆): 2(10.811 g/mol) + 6(1.008 g/mol)
Molar Mass (B₂H₆): 27.67 g/mol
1 B₂H₆ + 3 O₂ ---> 2 HBO₂ + 2 H₂O
^ ^
Molar Mass (H₂O): 15.998 g/mol + 2(1.008 g/mol)
Molar Mass (H₂O): 18.014 g/mol
3.7 g B₂H₆ 1 mole 2 moles H₂O 18.014 g
---------------- x --------------- x ----------------------- x ----------------- = 4.8 g H₂O
27.67 g 1 mole B₂H₆ 1 mole