Question

What is the mass of 7.46 x 10^23 formula units of NiCO3? A. 177 g NiCO3
B. 91.7 g NiCO3
C. 95.8 g NiCO3
D. 147 g NiCO3

Answer 1

The correct answer is option (D) 147 g NiCO3

Explanation :

• Since the molecular weight of $NiCO_3$ is :

    =$59 + 12 + 3\times 16$

    =$71 + 48$

    = 119 gm

• No of formula units of $NiCO_3$ in 1 mole = $6.022 \times 10^{23}$

• ∴Mass of 1 mole of $NiCO_3$ = 119 gm

     Or, mass of $6.022 \times 10^{23}$ formula units  of $NiCO_3$ = 119 gm

• So, mass of 1 formula unit of $NiCO_3 = \frac{119}{6.022 \times 10^{23}}$ gm
• Hence, mass of $7.46 \times 10^23$ formula units of $NiCO_3 = \frac{119}{6.022 \times 10^{23}}\times 7.46 \times 10^{23}$ gm

                      =147 gm

Hence , the mass of $7.46 \times 10^{23}$ formula units of NiCO3 is 147 gm .