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26.  The formula of the complex ion formed when aqueous zinc sulphate reacts with aqueous is given as:

Explain how the value x is determined

Zinc ion   ð  +2

Hydroxide ion ð -1x 4  = -4

X =-4+2 = -2

27. Copper can be obtained from copper(II)oxide using  carbon(II)oxide or coke

(a) Name another reagent that can be used to obtain copper from copper(II)oxide

  • Hydrogen

(b) The equation for the reaction with carbon (II) oxide is:

image

Calculate the mass of copper that would be obtained using 200dm3 of carbon (II) oxide.

 (Cu = 63.5, Molar Volume of gas  = 24.0 dm3)

We are given 200 dm3 of CO, which is equivalent to 200/24 = 8.33 moles of CO.

Since 1 mole of CuO reacts with 1 mole of CO to form 1 mole of Cu, we can expect to obtain 8.33 moles of Cu.

The mass of 8.33 moles of Cu can be calculated using its molar mass:

8.33 moles x 63.5 g/mole = 527.665 g or 528 g of copper.

Describe the correct procedure of heating a liquid in a test tube using a bunsen burner

  1. Obtain a test tube containing the liquid you wish to heat and place it in a test tube holder.
  2. Light the Bunsen burner using a lighter or a match, adjust the flame to obtain a blue flame which is hotter and cleaner than the yellow flame.
  3. Hold the test tube holder so that the test tube is above the Bunsen burner flame, but not touching it.
  4. Gently rotate the test tube to ensure that heat is evenly applied to the liquid. Avoid over-heating the liquid as it may cause it to boil over or crack the test tube.
  5. When the liquid reaches the desired temperature, remove the test tube from the heat source and place it on a heat-resistant surface.

Two allotropes of carbon are diamond and graphite

Explain why the density of diamond is higher than that of graphite

The density of diamond is higher than that of graphite because of differences in their molecular structures. Diamond is a three-dimensional crystal lattice structure made up of carbon atoms that are covalently bonded in a tetrahedral arrangement. This structure creates a highly packed arrangement of atoms, resulting in a high density.

On the other hand, graphite is composed of flat sheets of carbon atoms that are held together by weak van der Waals forces. The sheets can easily slide past each other, making graphite soft and slippery. The gaps between the sheets result in a lower density compared to diamond.

Additionally, the bonding in graphite is not as strong as that in diamond, leading to a looser arrangement of atoms and a lower density. These differences in molecular structure and bonding result in the differences in density between diamond and graphite.

Describe how water hardness can be removed by use of ion exchange resin

Water hardness can be removed through the process of ion exchange using an ion exchange resin. The ion exchange resin is a synthetic polymer that acts as a medium for exchanging ions. It works by exchanging hardness-causing ions such as calcium and magnesium with ions that do not contribute to hardness such as sodium.

The process of ion exchange works as follows:

  1. The hard water is passed through a tank filled with ion exchange resin beads.
  2. The hardness-causing ions in the water, such as calcium and magnesium, bond with the resin beads, releasing sodium ions in exchange.
  3. The water that has been stripped of hardness-causing ions then exits the tank and is collected as soft water.
  4. Over time, the resin beads will become saturated with hardness-causing ions and will need to be regenerated. This is typically done by washing the resin beads with a salt solution, which re-charges the resin with sodium ions.

Ion exchange is an effective method for removing water hardness because it can effectively reduce the concentration of hardness-causing ions to very low levels. Additionally, the process is relatively simple and can be automated, making it a convenient method for removing hardness from water in a variety of settings.