#### The transition metal ion $M^{2+}$ forms a green-coloured compound when combined with a ligand. If $0.025$ moles of $M^{2+}$ ions react with excess ligand, what mass of the green-coloured compound will be formed? (The compound's molar mass is 300 g/mol)Option: 1 7.5 gOption: 2  0.75 gOption: 3 75 gOption: 4 0.075 g

To determine the mass of the green-coloured compound formed, we need to use the concept of moles and molar mass. First, we calculate the number of moles of $M^{2+}$ions:

Number of moles $=$ given mass divided by the molar mass
Number of moles $= 0.025\, moles$
Since the $M^{2+}$ ions react with excess ligand, all the moles of $M^{2+}$ ions will form the green-coloured compound. Therefore, the number of moles of the green-coloured compound is also $0.025$ moles.

Now, we can calculate the mass of the compound using the equation:

Mass is calculated as moles multiplied by molar mass.
$Mass= 0.025 \ moles\: \times \: 300\ g/mol$
$Mass= 7.5 g$

Hence, the mass of the green-coloured compound formed is 7.5 grams. Therefore, the correct answer is option 1) 7.5 g.