Formula of a Hydrate
Post on 17-Feb-2016
135 Views
Preview:
DESCRIPTION
Transcript
Formula of a Hydrate
What is a hydrate?• An ionic compound that contains water
molecules in its structure• The formula states how many mol of
water molecules per one mol of ionic compound
• Example: CuSo4 5 H20Copper sulfate pentahydrate
What is an anhydrate?• The substance that remains after the
water is removed from a hydrate• Example: CuSo4
Anhydrous Copper sulfate
Prefixes1 mono2 di3 tri4 tetra5 penta6 hexa7 hepta8 octa9 nona10 deca
Steps to find formula1. Identify what’s given:
A. Hydrate/anhydrate (go to step 2)B. Anhydrate/water (skip to step 3)
2. If given hydrate and anhydrate, subtract to get water
3. Convert mass of anhydrate and water to moles of each, respectively
4. Find the ratio of water to anhydrate (in moles)5. Write the formula; ionic compound followed
by ratio of water6. Name the compound
Example 1
Step 2: 4.72g hydrate − 3.56g anhydrate
1.16g H2OStep 3: 3.56g CaCl2 1mol CaCl2
110.98g CaCl2 1.16g H2O 1mol H2O
18.02g H2O
Calcium chloride: Ca2+ Cl−
CaCl2
= 0.0321 molCaCl2
= 0.0644 mol H2O
SIG FIGS IN ANSWER MUST MATCH GIVEN!!
A calcium chloride hydrate has a mass of 4.72g. After heater for several minutes the mass of the anhydrate is found to be 3.56g. Determine the
formula and name of the hydrate.
Step 4: Ratio 0.0644 mol H2O 20.0321 mol CaCl2
Step 5: CaCl2 2H2O
Step 6: calcium chloride dihydrate
≈ 1
Example 2What is the formula an name for a hydrate which consists of 76.9% CaSO3 and 23.1% H2O?
SIG FIGS IN ANSWER MUST MATCH GIVEN!!
Step 3: 76.9g CaSO3 1mol CaSO3110.98g CaSO3
23.1g H2O 1mol H2O 18.02g H2O
= 0.640 mol CaSO3
= 1.28 mol H2O
Step 4: Ratio 1.28 mol H2O 20.640 mol CaSO3
Step 5: CaSO3 2H2O
Step 6: calcium sulfite dihydrate
≈ 1
top related