The type of hybridisation and bond angle in [Ni(CN)4]−2 are

The average atomic mass of M is 181.33 g/mol.

Explanation:

First off we need to know the reaction that takes place. The balanced reaction of M₂S₃(s) is:

The important section for this problem is this:

**Thus, the number of moles of M in M₂S₃ is equal to the number of moles of M in 2MO₂.

The decrease in mass means that M₂S₃ reacted and produced MO₂, thus the mass of MO₂ is 3.280-0.228=3.052 g

Now let's say x is the atomic weight of M, and write the molecular weights (Mw) of those two compounds:

Mw of M₂S₃= 2x + 96 g/mol

Mw of MO₂= x + 32 g/mol

Now we determine the moles of each compound, using the formula [ moles = mass / molecular weight ]:

Moles of M₂S₃=

Moles of MO₂=  

Using the equivalence marked by asterisks, we're left with (note that the second denominator is multiplied by 2 because of the reaction coefficients):

We solve for x:

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Thus, the average atomic mass of M is 181.33 g/mol.