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Questions in chemistry

📝 Answered - Step 2 Since the half-life is 30 years, then [tex]y(30)=[/tex] ______ 5 mg. Step 3 Thus, [tex]5=10 e^{30 k}[/tex], or [tex]e^{30 k}=[/tex] ______. Therefore, [tex]k=[/tex] ______.

📝 Answered - Draw the structure for the most stable chair conformation of cis-1-tert-butyl-3-chlorocyclohexane. Use the cyclohexane conformation drawing tool and guide points to draw each structure.

📝 Answered - Determine the usefulness and harmfulness of each given substance. | Substances | Usefulness | Harmfulness | |---|---|---| | baking soda | | | | sugar | | |

📝 Answered - How many hydrogen atoms can be bonded to one carbon atom? A. 2 B. 4 C. 1 D. 3

📝 Answered - $2 C_6 H_{14}+19 O_2 \rightarrow 12 CO_2+14 H_2 O$ The molar mass of each substance is provided in the table below. | Substance | Molar Mass $( g / mol )$ | | :------------------------- | :----------------- | | Hexane $\left( C _4 H _4\right)$ | 86.17 | | Oxygen $\left( O _2\right)$ | 32.00 | | Carbon dioxide $\left( CO _2\right)$ | 44.01 | | Water $\left( H _2 O \right)$ | 18.02 | What mass of oxygen would be needed?

📝 Answered - Select the correct answer. The average atomic mass of oxygen is 15.9994 amu. The atomic masses of its three isotopes are as follows: O-16: 15.995 amu; O-17: 16.999 amu; O-18: 17.999 amu. Which isotope is most likely to have the greatest abundance in nature? A. O-16 B. O-17 C. O-18

📝 Answered - Which of the following describes an endothermic reaction? A. [tex]$\Delta H_{f, \text { products }}=0$[/tex] B. [tex]$\Delta H_{ f }$, products $\ \textgreater \ \Delta H_{ f }$, reactants[/tex] C. [tex]$\Delta H_{ f }$, products $=H_{ f }$, reactants[/tex] D. [tex]$\Delta H_{ f }$, products $\ \textless \ \Delta H_{ f }$, reactants[/tex]

📝 Answered - Which one is a chemical change? (a) Evaporation of a liquid (b) Breaking of a brick (c) Burning of a candle (d) Moving of a wheel Chemical changes are (a) mostly irreversible (b) always reversible (c) always irreversible (d) mostly reversible Which one is not a physical change? (a) Dissolution of salt in water (b) Tearing a piece of paper (c) Melting of wax (d) Digestion of food During the dissolution of urea, heat (a) is evolved (b) is absorbed (c) does not change (d) none of these

📝 Answered - 7. Which of the following is a common solvent? A. ethanol B. water C. ether D. benzene 8. Select the correct answer in the following, which is involved in the definition of "like". A. The nature of the bonding B. Structure of solute C. Structure of solvent D. The nature of bonding, structure of solute and solvent

📝 Answered - Use the terms in the vocabulary box to fill in the blanks. Vocabulary box: Concentrated, Solution, Soluble, Insoluble, Water, Solvent, Solute, Homogeneous, Heterogeneous, Solution. 17. Homogeneous solution means to have the uniform or the same appearance. 18. While the _______ mixture means that different substances are mixed and are visible. 19. A mixture of two or more substances that is homogeneous is called _______. 20. The _______ is the larger part of the solution. 21. While the smaller part is what we call _______. 22. A solution that can easily dissolve in one another is _______. 23. And if the liquids are not soluble, they are called _______ solution. 24. A _______ is a solution that contains a large amount of solute relative to the amount that could dissolve. 25. Finally, the _______ is considered as the universal solvent for it can dissolve almost any solute.