Answer:
1) The mass of water lost = 7.7892 grams
2) Z = 3: Cu(NO3)2*3H2O
Explanation:
<u>Step 1: </u>Data given
Mass of copper (II) nitrate hydrate, Cu(NO3)2•zH2O = 34.8243 grams
Mass of substance after heating = 27.0351 grams
Molar mass of Cu(NO3)2 = 187.56 g/mol
Molar mass of H2O = 18.02 g/mol
<u>Step 2:</u> Calculate mass of water
The mass of water is the mass lost after heating.
Mass water = 34.8243 - 27.0351 = 7.7892 grams of water
<u>Step 3:</u> Calculate moles of Cu(NO3)2
Moles Cu(NO3)2 = Mass Cu(NO3)2 / Molar mass Cu(NO3)2
Moles Cu(NO3)2 = 27.0351 grams / 187.56 g/mol
Moles Cu(NO3)2 = 0.144 moles
<u>Step 4:</u> Calculate moles of H2O
Moles H2O = 7.7892 grams / 18.02 g/mol
Moles H2O = 0.432 moles
<u>Step 5:</u> Calculate Z
z = moles H2O / moles Cu(NO3)2
Z = 0.432/0.144
Z = 3
This means we have 3 water molecules in the formula. This makes the formula ofthe hydrate: Cu(NO3)2*3H2O
