1)How many moles of CO2 are in 225g of the NO2 gas? 2)How many grams are in 3.50 moles of K2Cr2O7?

Question

Urgent help needed

Answer 1

1) I'm going to assume that you meant 225g of CO₂, not NO₂.  If you meant NO₂ both times, the procedure will be the same (although the numbers will be different).  Note from your periodic table that C has an atomic mass of 12 and Oxygen has an atomic mass of 16.  Therefore, CO₂ has an atomic mass of 12+2(16) = 44.  That means there are 44 g CO₂ / mol CO₂.  So, we can run this one like a unit conversion problem:

 

225 g CO₂ * (1 mol CO₂ / 44 g CO₂) = 5.11 mol CO₂

 

2) Atomic masses:

K: 39

Cr: 52

O: 16

K₂Cr₂O₇: 2(39) + 2(52) + 7(16) = 294

 

3.50 mols K₂Cr₂O₇ * (294 g K₂Cr₂O₇ / 1 mol K₂Cr₂O₇) = 1030 g K₂Cr₂O₇