Question 1: Who was Dmitri Mendeleev and what was his main contribution to chemistry?

Answer: Dmitri Mendeleev was a Russian chemist who created the first periodic table organizing elements based on their properties and atomic weights.

Question 2: Explain the significance of Mendeleev's periodic law in organizing the elements.

Answer: Mendeleev's periodic law states that the properties of elements are a periodic function of their atomic weights, which allowed him to predict properties of undiscovered elements.

Question 1: Define the term 'periodic table'.

Answer: A chart that organizes chemical elements based on their atomic number and properties.

Question 2: Describe how Mendeleev predicted the properties of elements that were not yet discovered.

Answer: He left gaps in his periodic table and used the patterns of known elements to predict the properties of undiscovered elements.

Question 1: If a chemical plant produces 500 kg of sulfur using a process that yields 85% efficiency, how much sulfur is actually produced?

Answer: Actual amount = (Theoretical amount) x (Efficiency) = 500 kg x 0.85 = 425 kg

Question 2: A reactor contains 250 liters of a gas at standard temperature and pressure (STP). If the gas is nitrogen (molecular weight = 28 g/mol), how many moles of nitrogen are present?

Answer: Number of moles = (Volume in liters) / 22.4 L/mol = 250 / 22.4 ≈ 11.16 mol

Question 1: List three safety precautions to consider when handling chemicals in an industrial setting.

Answer: Wear protective gloves and goggles, work in a well-ventilated area, and follow proper disposal procedures.

Question 2: Describe a basic experiment to test the reactivity of a metal with acids, including the variables involved.

Answer: The experiment involves placing a sample of the metal in hydrochloric acid and observing the reaction. Variables include type of metal (independent), amount of acid (controlled), and temperature (controlled).

Question 1: A chemical company notices that the properties of elements in a specific group of the periodic table are similar. How does Mendeleev's arrangement explain this observation?

Answer: Mendeleev grouped elements with similar properties into the same columns, indicating periodicity based on element properties.

Question 1: Explain how Mendeleev's periodic table helped in discovering new elements and improving industrial processes.

Answer: Mendeleev's periodic table predicted the properties of undiscovered elements through gaps, guiding scientists to find new elements. This knowledge improved industries by allowing better material selection and chemical reactions.

Question 1: Discuss how understanding the periodic law is important for industries that produce chemical fertilizers.

Answer: It helps industries select the right elements like nitrogen, phosphorus, and potassium, and understand their properties to produce effective fertilizers.