Question

1- How many grams of H2S contain the same number of molecules as 13.9 g of BH3?

2- how many moles of n atoms are contained in 12 mol n2o5?

3- Refer to the periodic table and determine how many grams of sulfur contain the same number of atoms as 8.99 grams of phosphorus.

________g

Answer 1

1)

Molar mass of BH3,

MM = 1*MM(B) + 3*MM(H)

= 1*10.81 + 3*1.008

= 13.834 g/mol

mass(BH3)= 13.9 g

number of mol of BH3,

n = mass of BH3/molar mass of BH3

=(13.9 g)/(13.834 g/mol)

= 1.005 mol

For number of molecules to be same, number of mol should be same

So,

number of mol of H2S should also be 1.005 mol

Molar mass of H2S,

MM = 2*MM(H) + 1*MM(S)

= 2*1.008 + 1*32.07

= 34.086 g/mol

mass of H2S,

m = number of mol * molar mass

= 1.005 mol * 34.086 g/mol

= 34.3 g

Answer: 34.3 g

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