1)
We have 6 moles of C (2 x3=6), 10 moles of H (2 x 5=10) and 1 mole of S in 1 mole of (C₃H₅)₂S )
The molar mass of (C₃H₅)₂S is 114 g mol
atomic mass (C)=12 u
atomic mass (H)=1 u
atomic mass (S)=32 u
atomic weight ((C₃H₅)₂S )=2[3(12 u)+5( 1 u)]+32 u=114 u
molar mass=value of atomic weigth expres in g/ 1 mol
molar mass ((C₃H₅)₂S )=114 g/mol
we have to find the number of moles in 23.2 g of (C₃H₅)₂S )
114 g-------------------------1 mol
23.2 g------------------------ x
x=(23.2 g x 1 mol)/114 g≈0.2 moles
We calculate the number of moles of sulfur (S) in 23.2 g (≈0.2 moles) of (C₃H₅)₂S ).
1 mole of (C₃H₅)₂S )------------ 1 mole of S
0.2 moles of (C₃H₅)₂S )----------- x
x=(0.2 moles of (C₃H₅)₂S ) x 1 mole of S)/1 mole of (C₃H₅)₂S )=0.2 moles
Answer: we have 0.2 moles of sulfur in 23.2 gr of (C₃H₅)₂S )
2)
1 mole of any substance=6.022 x 10²³ atoms or molecules.
We have 10 moles of H in a mole of (C₃H₅)₂S )
1 mole of (C₃H₅)₂S )----------------------10 moles of H
0.75 moles of (C₃H₅)₂S )------------------ x
x=( 0.75 moles x 10 moles)/1 mole=7.5 moles
We compute the number of atoms in 7.5 moles of H
1 mole ---------------------------6.022 x 10²³ atoms
7.5 moles------------------------ x
x=(7.5 moles x 6.022 x 10²³ atoms)/1 mole=4.52 x 10²⁴ atoms.
answer: we have 4.52 x10²⁴ atoms of H in 0.75 moles of (C₃H₅)₂S )
3)
We have to calculate the number of moles in 4.20 x 10²³molecules of (C₃H₅)₂S )
1 mole---------------------------6.022 x 10²³ molecules
x-----------------------------------4.20 x 10²³ molecules
x=(1 mole x 4.20*10²³)/6.022*10²³ molecules≈0.697 moles
we have 72 g of C in 1 mole of (C₃H₅)₂S ).
number of grams in 1 mole of (C₃H₅)₂S )=2*3*12 g=72 g
1 mole of (C₃H₅)₂S )----------------72 g of C
0.697 moles of (C₃H₅)₂S )---------- x
x=(0.697 moles * 72 g)/1 mole≈50.18 g
Answer: there are 50.18 g of C in 4.20*10²³ molecules of (C₃H₅)₂S )
4)
We have to calculate the number of moles in 15 g of (C₃H₅)₂S )
114 g of (C₃H₅)₂S )-------------------- 1 mole of (C₃H₅)₂S )
15 g of (C₃H₅)₂S )----------------------- x
x=(15 g * 1 mole)/114 g=0.1316 moles of (C₃H₅)₂S )
We calculate the number of moles of C in 0.1316 moles of (C₃H₅)₂S )
1 mole of (C₃H₅)₂S )------------------6 moles of C
0.1316 moles of (C₃H₅)₂S )--------- x
x=(0.1316 moles * 6 moles)/1 mole=0.7895 moles
We calculate the number of atoms in 0.7895 moles of C
1 mole of C --------------------------------- 6.023*10²³ atoms of C
0.7895 moles of C------------------------- x
x=(0.7895 moles * 6.022*10²³)/1 mole≈4.75*10²³ atoms.
Answer: there are 4.75*10²³ atoms of C in 15 g of (C₃H₅)₂S )
Other way:
We calculate the number of molecules in 15 g of (C₃H₅)₂S )
114 g of (C₃H₅)₂S )---------------6.023*10²³ molecules of (C₃H₅)₂S )
15 g of (C₃H₅)₂S )----------------x
x=(15 g* 6.022*10²³ molecules)/114 g=7.9237 *10²² molecules
A molecule of (C₃H₅)₂S ) have 6 atoms of C; therefore
1 molecule---------------------------6 atoms of C
7.9237 *10²² molecules----------- x
x=(7.9237*10²² molecules * 6 atoms)/1 molecule=4.75*10²³ atoms
We have the same answer: there are 4.75*10²³ atoms of C in 15 g of (C₃H₅)₂S )