This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here are the answers to the questions: 13. Water droplets formed on a cold surface after breathing out show that the lungs remove water vapor. When warm, moist air from the lungs comes into contact with a cold surface, the water vapor condenses into liquid droplets. A) water vapour 14. The main reason living organisms respire is to release energy for life processes. Respiration breaks down glucose to produce ATP, which powers cellular activities. D) release energy for life processes 15. To calculate the molar mass of ammonia, NH_3: Step 1: Identify the atomic masses of nitrogen (N) and hydrogen (H). Given: N = 14, H = 1 Step 2: Sum the atomic masses for each atom in the formula. Molar mass of NH_3 = (1 × Molar mass of N) + (3 × Molar mass of H) Molar mass of NH_3 = (1 × 14) + (3 × 1) Molar mass of NH_3 = 14 + 3 Molar mass of NH_3 = 17 g mol^-1 B) 17 g mol^-1 16. A buffer solution is important in chemical reactions because it maintains a nearly constant pH. Buffers resist significant changes in pH when small amounts of acid or base are added. D) maintains a nearly constant pH 17. The observation that best confirms a substance is a base is that it turns red litmus paper to blue. Acids turn blue litmus red, while bases turn red litmus blue. B) turns red litmus paper to blue 18. When salt dissolves completely in water to form a clear solution, the mixture is best described as a homogeneous mixture. In a homogeneous mixture, the components are uniformly distributed throughout. A) a homogeneous mixture 19. The atom is regarded as the basic unit of matter because it retains the chemical properties of an element. It is the smallest particle of an element that still exhibits the characteristic chemical behavior of that element. B) retains the chemical properties of an element 20. In basic science, the states of matter commonly studied are solid, liquid, and gas, which are three states of matter. C) three states of matter 21. To calculate the density of the metal block: Step 1: Recall the formula for density. Density = MassVolume Step 2: Substitute the given values. Density = 75 g39 cm^3 Step 3: Calculate the density. Density ≈ 1.923 g/cm^3 Rounding to two decimal places, the density is 1.92 g/cm^3. D) 1.92 g cm^-3 22. Among the given options, mass is a fundamental quantity. Force, volume, and weight are derived quantities, meaning they can be expressed in terms of fundamental quantities. A) Mass 23. A chemical bottle labelled with a fire symbol (flame pictogram) indicates that the substance is flammable. C) flammable 24. The activity that best illustrates the harmful use of scientific knowledge is the use of DDT to kill fish in rivers. DDT is a pesticide that was found to be highly toxic to aquatic life and the environment, demonstrating a negative impact of scientific application. D) Use of DDT to kill fish in rivers 25. The correct sequence in the application of the scientific method during an investigation is to first form a hypothesis, then conduct experimentation to test it, and finally, the results contribute to scientific knowledge. C) Hypothesis → Experimentation → Scientific knowledge That's 2 down. 3 left today — send the next one.