1.26 A covalent molecule M contains four shared pairs of electrons. What is M?   A hydrogen chloride, HCl B methane, CH4 C ammonia, NH3 D water, H2O

1.38 River water contains soluble impurities, insoluble impurities, and bacteria. River water is made safe to drink by filtration and chlorination. Which statement is correct?

1.34 Which is a chemical change?

  QUESTION 3 3.1   Chlorine exists as a number of different isotopes. What is meant by the term isotopes? [2] 3.2   A chloride ion has a symbol shown.   Right-click on the button to open the data booklet in a new tab.            a How many neutrons are contained in this chloride ion? [1]   b How is a chloride ion formed from the chlorine atom? [1]   c Which atom forms an ion with a 1+ charge and has the same number of electrons as Cl-? [1]       [5]  

1.27 An isotope of chromium has an atomic mass of 52g.mol-1 . Which statement about an atom of this isotope of chromium is correct?

1.28 During the electrolysis of concentrated hydrochloric acid, gases are produced at both electrodes. Which statement describes the test result for the gas collected at the negative electrode?

1.19 Which statement about aluminium is not correct?

1.39 Which physical property is used to separate the nitrogen and oxygen from air?

1.14 Three gas jars contain carbon dioxide, hydrogen, and oxygen. Which one of the following tests could be used to discover which gas is in each jar?

1.11 The diagram shows the reaction between zinc oxide and dilute hydrochloric acid.   Right-click on the button to open the data booklet in a new tab.        Which terms describe the reaction?   Endothermic Neutralization A Yes Yes B Yes No C No Yes D No No