Question

1. Number of Atoms in 2.5 gram of MgCl2

2. Write a complete and net Ionic equation for the following chemical reaction.

Pb(NO3)2(aq) + 2NaBr(aq) ----> PbBr2(S) + 2NaNO3(aq)

Complete Ionic equation:

Net Ionic equation:

3. FeS3 + HCl --->

4. Mg + BiCl3 --->

Answer 1

1.as we see there are 3 moles of atoms present in MgCl2.

Molecular Mass of Mg = 24.3g and Molecular Mass of Cl=35.5 ( approx). So Molecular Mass of MgCl2= 24.3+( 2*35.5)= 95.3g.

So 95.3g contains 3 mole of atoms i.e., 3* Avogadro's no. ( 3*6.023*10^23).

=> 95.3g= 18.069*10²³

1g= 18.069*10²³/95.3

=> 2.5g =[ 18.069*10²³/95.3]*2.5

= 0.474*10²³ atoms

2- Lead(II) nitrate, Pb(NO3)2, and sodium bromide, NaBr, are soluble in aqueous solutions that is they dissociate completely to form cations and anions in water .here it goes as follows

Pb(NO3)2(aq)→Pb2+(aq)+2NO−3(aq)

NaBr(aq)→Na+(aq)+Br−(aq)

When these two solutions are mixed, lead(II) bromide, PbBr2, an insoluble ionic compound and sodium nitrate, NaNO3, another soluble ionic compound, will be formed.

The complete balanced ionic equation is given as

Pb2+(aq)+2NO−3(aq)+2×[Na+(aq)+Br−(aq)]→PbBr2(s)⏐⏐ ⏐↓+2×[Na+(aq)+NO−3(aq)]

Remember that nitrate anions, NO−3, and the sodium cations, Na+, exist as ions on both sides of the equation.so they will get cancel in net equation.

So the net equation is given as

Pb2+(aq)+2Br−(aq)→PbBr2(s)

3 - FeS3 +3HCl --->FeCl3 + 3HS

Fe3+ + 3S- + 3H⁺ + 3Cl- ---> Fe3+ + 3Cl- + 3HS

=> 3H⁺ + 3S^- ----> 3HS

4.Overall reaction is given by

3Mg (s)+2BiCl3--->3MgCl2 + 2Bi (s)

Ionic form

3Mg(s) + 2Bi3+ + 6Cl- ---> 3Mg2+ + 6Cl- + 2Bi (s)

Thank u