A student found this information about hydrogen.(a) (i) The student repeated Boyle’s experiment using iron and dilute sulfuric acidState two observations that he could have made1.2.(iii) Complete the word equation for this reaction.Iron + sulfuric acid → +(b) Balance the equation for the complete combustion of hydrogen.H2 + O2 → H2O(c) To show that the liquid produced by burning hydrogen was pure water, a student carried out achemical test and a physical test.(i) The chemical test involves adding a few drops of the liquid to a sample of anhydrous copper(II) sulfate. State the colour change observed.Initial colourFinal colour(ii) Place a cross (  ) in one box to show the formula of the compound formed in this chemical test. A Cu(OH ) 2 B CuSO4 C CuSO4H2O D CuSO4 . 5H2O(iii) The physical test involved measuring a property of the liquid.State a suitable physical property and give the value for pure water.Physical propertyValue(c) (i) suggest what property of hydrogen makes it suitable for filling balloons.(iii) Helium is now used instead of hydrogen to fill balloons.State the property of helium that makes it more suitable than hydrogen for filling balloons.(d) Write an equation, including state symbols, to show the process that occurs when hydrogen isliquefied.Ammonium chloride contains oppositely charged ions(a) State the formula of each ionPositive ionNegative ion(b) (i) Describe a chemical test to show that a substance contains ammonium ions.(ii) describe a chemical test to show that a substance contains chloride ions.(c) Ammonium chloride decomposes when heated:NH4CI(s) ⇄ NH3(g) + HCI(g)What does the ⇄ symbol indicate about the reaction?(d) The reaction between ammonia and hydrogen chloride can be used to illustrate diffusion withthe following apparatus.After a few minutes, a white solid appears inside the tube(i) Identify the white solid(ii) What does the diagram show about the speed of the ammonia molecules compared to thespeed of the hydrogen chloride molecules?(e) State the main hazard when using concentrated hydrochloric acid in the experiment in (d)suggest one precaution you could use to minimise this hazard.HazardPrecaution

(a) (i) Two observations that the student could have made are:

1. The iron would start to dissolve in the sulfuric acid.
2. The solution would start to bubble or fizz, indicating the release of a gas.

(iii) The word equation for this reaction is: Iron + sulfuric acid → Iron sulfate + Hydrogen

(b) The balanced equation for the complete combustion of hydrogen is: 2H2 + O2 → 2H2O

(c) (i) The chemical test involves adding a few drops of the liquid to a sample of anhydrous copper(II) sulfate. The colour change observed would be: Initial colour: White Final colour: Blue

(ii) The formula of the compound formed in this chemical test is: D CuSO4 . 5H2O

(iii) A suitable physical property to measure would be boiling point, and the value for pure water is 100 degrees Celsius.

(c) (i) The property of hydrogen that makes it suitable for filling balloons is its low density.

(iii) The property of helium that makes it more suitable than hydrogen for filling balloons is that it is non-flammable.

(d) The equation to show the process that occurs when hydrogen is liquefied is: H2(g) → H2(l)

Ammonium chloride contains oppositely charged ions

(a) The formula of each ion is: Positive ion: NH4+ Negative ion: Cl-

(b) (i) A chemical test to show that a substance contains ammonium ions is to heat the substance with sodium hydroxide solution. If ammonium ions are present, ammonia gas will be released, which can be detected by its characteristic pungent smell.

(ii) A chemical test to show that a substance contains chloride ions is to add silver nitrate solution. If chloride ions are present, a white precipitate of silver chloride will form.

(c) The ⇄ symbol in the equation NH4CI(s) ⇄ NH3(g) + HCI(g) indicates that the reaction is reversible, meaning it can proceed in both the forward and reverse directions.

(d) (i) The white solid that appears inside the tube is ammonium chloride.

(ii) The diagram shows that the ammonia molecules move faster than the hydrogen chloride molecules, as the white ring of ammonium chloride forms closer to the hydrogen chloride end of the tube.

(e) The main hazard when using concentrated hydrochloric acid in the experiment is that it is corrosive and can cause burns. A precaution to minimise this hazard is to wear protective clothing, including gloves and safety goggles.