Answer:
B, 1.98g
Step-by-step explanation:
No. of moles = mass / molar mass
no. of moles of Na2SO3 produced = 1.2 / 126.05 =0.009520031mol
From the balanced equation, the mole ratio of NaHSO3:Na2SO3 = 2:1, meaning every 2 moles of NaHSO3 reacted, gives out 1 mole of Na2SO3.
Since 0.009520031mol of Na2SO3 is produced, the no. of moles of NaHSO3 used = 0.009520031 x 2
= 0.019040063 mol
Mass = no. of moles x molar mass
Hence,
mass of NaHSO3 used = 0.019040063 x 104.07
= 1.98 g
= B