Question

How many moles of Chromium are present 85 grams of Chromium (II) Sulphide ?
(Cr - 52) (S - 32)

Answer 1

Explanation:

Molecular weight of Cr₂S₃ is 200 g.

200 g of Cr₂S₃ contains = 104 g of Cr

85 g of Cr₂S₃ contains = (104 × 85)/200 g of Cr

Ans: 44.2 g

Number of moles of Cr = 42.2/52

Ans: 0.85 moles of Cr

Must know:

Weight of an element = No. g-atoms × Gram atomic weight

Number of moles = Weight/Gram atomic weight

Number of gram-atoms = Weight of an element in grams/Gram atomic weight

Answer 2

$\huge\bf\color{blue}Answer:$

Molecular mass of Cr₂S₃

$\bf\color{red}=>2 × 52 + 3 × 32 = 200g$

Now, 200 g of Cr₂S₃ contains

$\bf\color{red}=> 104 g \ of \ Cr$

So, 85 g of Cr₂S₃ will contain

$\bf\color{red} =>104 × 85/200 = 44.2 g \ of \ Cr$

Hence, number of moles of Cr

$\bf\color{red}==>44.2 /52 = 0.85 \ moles$