Question 1: Group 1 elements are known as alkali metals. List three common properties of alkali metals.

Answer: They are highly reactive, soft, and have low melting points.

Question 2: Explain why alkali metals are stored under oil in laboratories.

Answer: To prevent reaction with moisture and oxygen in the air.

Question 1: Calculate the molar mass of sodium (Na). Given atomic mass: Na = 23 g/mol.

Answer: 23 g/mol

Question 2: A sample contains 46 grams of potassium (K). How many moles of potassium are present? Atomic mass of K = 39 g/mol. Show your working.

Answer: 1.18 moles

Question 3: If 2 grams of lithium (Li) reacts with water, calculate the number of moles of lithium reacted. Atomic mass of Li = 7 g/mol.

Answer: 0.286 moles

Question 1: Outline the key safety precautions when storing and handling alkali metals in a laboratory.

Answer: Use of oil for storage, wearing safety goggles and gloves, working in a fume cupboard, handling with tongs, and avoiding contact with moisture and oxygen.

Question 2: Describe a simple experimental procedure to test the reactivity of sodium with water, including the variables and safety precautions.

Answer: Place a small piece of sodium in a container of distilled water. Observe the reaction (e.g., effervescence, melting). Variables include the size of sodium and temperature of water. Safety precautions: Wear safety goggles and gloves, perform in a fume cupboard, and handle sodium with tongs to avoid burns or contact with moisture.

Question 1: A series of experiments measured the reactivity of lithium, sodium, and potassium with water, recording the time taken for the reaction to complete. Lithium reacted in 30 seconds, sodium in 15 seconds, and potassium in 5 seconds. Explain the trend observed and relate it to atomic structure.

Answer: The reactivity increases down Group 1 because the outer electron is further from the nucleus, making it easier to lose. Lithium has the smallest atomic radius, so it reacts slower, while potassium has the largest radius and reacts fastest.

Question 1: Explain why sodium vapour lamps are used for street lighting and how they relate to the properties of sodium.

Answer: Sodium vapour lamps emit a bright yellow light because sodium atoms produce a characteristic yellow emission line when excited, making them effective for street lighting due to high visibility.

Question 2: Calculate the empirical formula of an alkali metal oxide if 4.0 g of the metal reacts with 8.0 g of oxygen.

Answer: The empirical formula is MO.

Question 3: Describe how alkali metals are used in the manufacture of batteries and the advantages of using them in this application.

Answer: Alkali metals like lithium are used in rechargeable batteries (lithium-ion batteries) because they have high electrochemical potential and lightweight properties. They enable high energy density, long cycle life, and are suitable for portable electronic devices and electric vehicles.