What is the minimum amount of water is needed to dissolve 3.0 mol potassium dichromate (k2cr2o7)

6.79 litres

Explanation:

Potassium dichromate is K2Cr2O7

Its molar mass = 294.18 g/mol

If,

1 mole = 294.18 g

3 mole = 3 x 294.18 g

= 882.54 g

Solubility of K2Cr2O7 is

4.9 g/100 mL at 0⁰c

13 g/100 mL at 20⁰c

102 g/100 mL at 100⁰c

No specific temperature is given so I have used 20⁰C since it is close to room temperature.

at 20⁰C:

13 g of K2Cr2O7 would dissolve in = 100 mL

So 1 g of K2Cr2O7 dissolves in = (100/13)

= 7.692

882.54 g of K2Cr2O7 dissolves in = 882.54 x 7.692

= 6788.59mL

We convert to litres

= 6.79 L

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.