Question

A hydrate of iron (lll) thiocyanat $Fe{\left( {SCN} \right)_3}$ , was found to contain 19% ${H_2}O$ . What is the formula of the hydrate.

Answer 1

Hint : A hydrate is a compound that comprises water or its component components in chemistry. The chemical state of water varies greatly among the many groups of hydrates, some of which were named as such before their chemical structure was discovered.

Complete Step By Step Answer:
The procedures for determining a hydrate's formula are as follows.
Calculate the volume of water that has escaped the compound. This enables us to calculate the quantity of water in the hydrate as well as the mass of the anhydrate. We achieve this by subtracting the anhydrate's mass from the hydrate's mass. This is the same as the volume of water. Convert the amount of water in gallons to moles. To acquire moles of water, divide the mass of water by the molar mass of water. Remember that molar mass is measured in g/mol. When we divide mass (in grammes) by molar mass (g/mol), grammes cancel out, leaving us with moles. Convert the remaining mass of anhydrate to moles. To determine the moles of anhydrate, divide the mass of anhydrate by the molar mass of anhydrate. Calculate the mole ratio of water to anhydrate. You'll have more fluids than anhydrate in most cases, therefore divide the moles of water by the moles of anhydrate. This is how you find out what your mole ratio is. To write the formula, use the mole ratio.
Hence here in ${{Fe}}{\left( {{{SCN}}} \right)_{{3}}}{{.m}}{{{H}}_{{2}}}{{O}}$
Molecular weight of hydrate =$56 + 3 \times (32+12+14) + 18m = 230 + 18m$
${{\% of }}{{{H}}_{{2}}}{{O = }}\dfrac{{{{n \times Molar\;mass\;of }}{{{H}}_{{2}}}{{O}}}}{{{{Molarmass\;of\;molecule + n} \times {Molar\;mass\;of }}{{{H}}_{{2}}}{{O}}}} \times 100$
$\% {{ }}of{{ }}{{{H}}_2}{{O}} = \dfrac{{18\;{{m}} \times 100}}{{230 + 18\;{{m}}}} = 19$
Hence
M = 3
Hence here in ${{Fe}}{\left( {{{SCN}}} \right)_{{3}}}{{.m}}{{{H}}_{{2}}}{{O}}$ it Is now ${{Fe}}{\left( {{{SCN}}} \right)_{{3}}}{{.3}}{{{H}}_{{2}}}{{O}}$ .

Note :
The anion [ $SC{N^ - }$ ] is thiocyanate (also known as rhodanide). It's thiocyanic acid's conjugate base. The colourless compounds potassium thiocyanate and sodium thiocyanate are common derivatives. Thiocyanates are organic compounds that contain the functional group SCN. Pyrotechnics previously utilised mercury(II) thiocyanate.