Final answer:
Without specific data related to an experiment or a reaction involving K2C2O4.H2O, it is impossible to determine the amount of it in the salt mixture from the information provided.
Step-by-step explanation:
The question does not provide enough information to determine how much K2C2O4.H2O is in the salt mixture. To answer a question like this, we would need specific data related to an experiment or a reaction involving K2C2O4.H2O, such as a description of a laboratory process, provided masses of reactants and products, or equilibrium concentrations to calculate the amount of it in the mixture. Since none of the information given in the question mentions K2C2O4.H2O, it's impossible to calculate its quantity accurately.