Question

(a) A list of formulae is shown.
           CH $_{4}$         Cl $_{2}$         MgCl $_{2}$            N$_{2}$           NaCl             NH $_{3}$           O$_{2}$
Identify the formula from the list which represents:
(i) a compound that is the main constituent of natural gas
(ii) an element that bleaches damp litmus paper
(iii) an element that makes up 21% of clean air
(iv) a compound containing an ion with a 1+ charge
(v) a gas made by displacement from an ammonium salt.

(b) A student investigates the rate of reaction between excess dilute hydrochloric acid and powdered magnesium carbonate.
Carbon dioxide gas is produced in this reaction.
Fig. 2.1 shows the apparatus the student uses.

The student measures the mass of the conical flask and its contents during the reaction.
(i) Explain why the mass of the conical flask and its contents decreases during the reaction.
(ii) The student wants to increase the rate of reaction. They do not change the particle size of the magnesium carbonate.
State two changes to the reaction conditions that the student makes to increase the rate of reaction.

iii) Complete the word equation for the reaction

c) Magnesium chloride is soluble in water.
State the separation technique used to obtain solid magnesium chloride from a solution of magnesium chloride.