Which of the following substances is not a mixture?

Here are the solutions to the questions from the image: 1. Consider the following chemical equation: MgCl_2 · 6H_2O MgCl_2 + 6H_2O The reaction represented by the equation is Step 1: Analyze the given reaction. The reactant is a hydrated salt, magnesium chloride hexahydrate (MgCl_2 · 6H_2O). The products are anhydrous magnesium chloride (MgCl_2) and water (H_2O). Step 2: Identify the process. The reaction shows the removal of water of crystallization from a hydrated compound. This process is known as dehydration. Step 3: Compare with the given options. A. Hydrolysis: Reaction with water to break a compound. B. Hydration: Addition of water. C. Neutralization: Reaction between an acid and a base. D. Dehydration: Removal of water. The correct option is D. D) dehydration 2. The preparation of carbon(II) oxide is done in a fume cupboard because the gas is Step 1: Identify carbon(II) oxide. Carbon(II) oxide is the chemical name for carbon monoxide (CO). Step 2: Recall the properties of carbon monoxide. Carbon monoxide is a colorless, odorless, and highly poisonous gas. Step 3: Determine why a fume cupboard is necessary. Due to its poisonous nature, carbon monoxide must be handled in a fume cupboard to prevent inhalation and ensure safety. The correct option is B. B) poisonous 3. Which of the following substances is not a mixture? Step 1: Define a mixture. A mixture is a substance containing two or more different substances that are not chemically bonded together. Step 2: Evaluate each option: A. Iron rod: An iron rod is primarily composed of the element iron. While commercial iron might contain impurities or be an alloy (which is a mixture), in the context of these options, pure iron is an element, not a mixture. B. Urine: A complex biological fluid containing water, urea, salts, and other dissolved substances, making it a mixture. C. Sea water: A solution of various salts (like sodium chloride) dissolved in water, making it a mixture. D. Brine: A concentrated solution of salt (usually sodium chloride) in water, making it a mixture. Step 3: Conclude which is not a mixture. Among the given options, an iron rod (representing the element iron) is the only one that is not inherently a mixture. The correct option is A. A) Iron rod 4. Carbon(IV) oxide could be produced from glucose by Step 1: Identify carbon(IV) oxide. Carbon(IV) oxide is carbon dioxide (CO_2). Step 2: Consider the processes that produce CO_2 from glucose (C_6H_12O_6). Fermentation: This is an anaerobic process where microorganisms convert glucose into ethanol and carbon dioxide (e.g., alcoholic fermentation: C_6H_12O_6 2C_2H_5OH + 2CO_2). Oxidation (Cellular Respiration): Glucose is oxidized to CO_2 and water in the presence of oxygen. Decarboxylation: A specific reaction where a carboxyl group is removed, releasing CO_2. This is a step within broader processes like fermentation or respiration. Step 3: Choose the most appropriate option. While oxidation and decarboxylation are involved, fermentation is a direct and common biological process specifically known for producing CO_2 from glucose. The correct option is C. C) fermentation 5. If carbon forms CX_4 and CY_2 with elements X and Y respectively, the formula of the compound that would be formed between elements X and Y is Step 1: Determine the valency of element X. In CX_4, carbon (valency 4) combines with four atoms of X. This means X has a valency of 1. Step 2: Determine the valency of element Y. In CY_2, carbon (valency 4) combines with two atoms of Y. This means Y has a valency of 2. Step 3: Determine the formula of the compound formed between X (valency 1) and Y (valency 2). Using the criss-cross method, the valency of X (1) becomes the subscript for Y, and the valency of Y (2) becomes the subscript for X. Step 4: Write the formula. The compound formed would be X_2Y. The correct option is D. D) X_2Y 6. When the pressure on 200 cm^3 of a gas is doubled, and its absolute temperature is halved, its volume would become Step 1: State the combined gas law formula. (P_1V_1)/(T_1) = (P_2V_2)/(T_2) where P is pressure, V is volume, and T is absolute temperature. Step 2: Identify the initial conditions (P_1, V_1, T_1) and final conditions (P_2, V_2, T_2). Initial volume V_1 = 200 cm^3. Let initial pressure P_1 = P. Let initial absolute temperature T_1 = T. Final pressure P_2 = 2P (pressure is doubled). Final absolute temperature T_2 = (T)/(2) (absolute temperature is halved). We need to find the final volume V_2. Step 3: Substitute the values into the combined gas law equation. (P · 200)/(T) = ((2P) · V_2)/((T/2)) Step 4: Simplify the equation to solve for V_2. (200P)/(T) = (4P · V_2)/(T) Multiply both sides by T: 200P = 4P · V_2 Divide both sides by P: 200 = 4V_2 V_2 = (200)/(4) V_2 = 50 cm^3 The correct option is C. C) 50 cm^3 What's next? Send 'em!