Question | Answer |
What ions are in hard water? | Ca+2 and Mg+2 |
What is the effect of hard water? | Produces Scum and Scale |
What is Scale? | the deposit left behind after boiling the kettle in a hard-water area. It is Calcium Carbonate |
What is Scum? | The deposit made from soap reacting with the Ca+2 ions |
Which type of water creates the most lather with soap: hard or soft water? | Soft |
What is temporary hardness? | Caused by having bicarbonate ions dissolved in water |
What is permanent hardness? | Caused by having sulfate ions dissolved in water |
How can you remove temporary hardness? | Simply boiling |
How can you remove permanent hardness? | Ion exchange |
How does ion exchange work? | where Ca+2 ion are replacing Na+ on a resin; the Na+ ions are replacing the Ca+2 in water |
Why should you treat your water if you live in a hard-water area? | Overtime, limescale will build up in washing machine pipes and block them |
Why does the water become hard again after having used an ion-exchange resin for a while? | All the Na+ions have been replaced on the resin |
How do you regenerate the resin? | Pass a concentrated brine (NaCl solution) through the resin will force the Ca+2 out of the resin and the resin will carry Na+ ions again |
What is the concentration of calcium ions in a sample of water that has: 0.4 g of calcium ions dissolved in 2 dm3 of the water | 0.4/2=0.2 gdm−3 |
What is the concentration of calcium ions in a sample of water that has: 0.25 g of calcium ions dissolved in 5 dm3 of the water? | 0.25/5=0.05 gdm−3 |
A sample of hard water has a concentration of calcium ions of 0.12 g dm-3. What mass of calcium ions would there be in a 200 cm3 glass of the water? | 0.12 x 0.2dm3 = 0.024g |
What is the formula to work out concentration? | concentration (g.dm-3) = mass(g) / volume(dm3) |