Question

1. 26 mol of P₄O₁₀ contains how many moles of P?

? mol P

2. How many moles of N are in 0.247 g of H₂O?

? mol N

3. How many total atoms are in 0.870 g of P₂O₅?

? atoms

Answer 1

1. 1 mole of P₄O₁₀ contains--------------------------- 4 moles of P

26 moles of P₄O₁₀ contains-----------------------------? moles of P

= (26 moles * 4 moles)/ 1 mole

= 104 moles of P

2. How many moles of N are in 0.247 g of H₂O?

No. moles of N in H2O is zero.          (since H2O is not having N -atoms in its formula)

If it is no.of H-moles then it is as follows:

18g of H2O contains--------------- 2 moles of H                    (since the molecular mass of water is 18g/mol)

then 0.247g contains ---------------? moles of H

= (0.247g * 2 moles)/ 18g

= 0.0274 moles of H.

3. How many total atoms are in 0.870 g of P₂O₅?

sol: 1 mole of P2O5 weighs------------------(31+31+5*16)g= 142g

Hence 142g of P2O5 contains------------------- (2+5)moles

                                                                        7 * 6.023*10^23 atoms

then 0.870 grams of P2O5 contains -------------? atoms

= (0.87g * 7 * 6.023*10^23 atoms)/ 142g

= 0.258 * 10^23 atoms

= 2.58 * 10^23 atoms