gA scientist is trying to discover information about an unknown metal in a compound. The formula for the compound is believed to be XBr3XBr3 where XX is the unknown metal. The scientist determined that a 4.700 g4.700 g sample of this compound contains 4.834×10−2 mol Br4.834×10−2 mol Br . Calculate the atomic mass of the unknown metal, XX .

Solution :

It is given that :

The formula of the compound =

And that 4.70 g of the sample contains mol of Br.

It means that :

1 mol of contains = 3 mol of Br

∴ 3 mol of contain in 1 mol of

mol of  contains mol of

Thus the mol of = mol

The given mass is = 4.700 g

Therefore, the of  

                                                          = 298.4 g/mol

So of = of X + 3 x of Br

      298.4 g/mol = of X + 3 x 79.90 g/mol

      298.4 g/mol = of X + 239.7 g/mol

        of X = 58.71 g/mol    (since 1 amu = 1 g/mol)      

Therefore the atomic mass of the unknown metal = 58.71 g/mol

So the unknown meta is Nickel.

2b2t

explanation:

2b2t

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.