100 liters of water for softening needed 15.9 grams of #Na_2CO_3#. What was the hardness of water? Chemistry 1 Answer il maestro Mar 22, 2018 15 °f Explanation: 15.9 gr of # Na_2CO_3# are 0.15 moles, therefore the 100 liters softened water contain 0.15 moles of #CaCO_3#, i.e. 1.5 millimolar Calcium ion, corresponding to 15 french degrees (moderately hard water) Answer link Related questions How do I determine the molecular shape of a molecule? What is the lewis structure for co2? What is the lewis structure for hcn? How is vsepr used to classify molecules? What are the units used for the ideal gas law? How does Charle's law relate to breathing? What is the ideal gas law constant? How do you calculate the ideal gas law constant? How do you find density in the ideal gas law? Does ideal gas law apply to liquids? Impact of this question 1318 views around the world You can reuse this answer Creative Commons License