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Questions in chemistry

[Done] Which of the following is green in colour? A) Mn2O7 B) PbCrO4 C) Ag2CrO4 D) K2Cr2O7

[Done] State four effects of petrochemicals on the environment.

[Done] One isotope of sodium has 11 protons and 7 neutrons. What is the mass number of this isotope? A. 4 B. 7 C. 11 D. 18

[Done] Which statement is usually true about the relationship between activation energy and reaction rates? A. Low activation energy barriers result in low rates. B. High activation energy barriers result in low rates. C. Low activation energy barriers result in no reaction. D. High activation energy barriers result in no reaction.

[Done] The equation for the pH of a substance is [tex]$pH = -\log [H^+]$[/tex], where [tex]$H^+$[/tex] is the concentration of hydrogen ions. Which equation models the concentration of hydrogen ions ([tex]$H^+$[/tex]) of a solution whose pH is 7.2? A. [tex]$[H^+] = \log 7.2$[/tex] B. [tex]$[H^+] = -\log 7.2$[/tex] C. [tex]$[H^+] = 10^{-7.2}$[/tex] D. [tex]$[H^+] = 10^{7.2}$[/tex]

[Done] Which of the following is an incorrect representation for a neutral atom? (a) ${ }_3^6 Li $ (b) ${ }_6^{13} C$ (c) ${ }_{30}^{63} Cu$ (d) ${ }_{15}^{30} P$ (e) ${ }_{47}^{108} Ag$

[Done] Consider the following chemical reaction of bromothymol blue indicator. It appears yellow in undissociated form and blue in its dissociated aqueous solution. [tex]\underset{\substack{HC_2 H_3 O_2(a q) \\ \text { yellow }}}{\stackrel{+}{C_2} H_3 O_2^{-}(a q)} \text { blue }[/tex] What will be the color of the solution if a large amount of [tex]H _2 CO _3[/tex] is added? A. The solution will remain yellow. B. The solution will turn blue. C. The solution will turn pink. D. The solution will turn green.

[Done] Which is the best definition of activation energy? A. the energy required to end a chemical reaction B. the energy required to bind a substrate to an active site C. the energy required to form or break the bonds of reactant molecules D. the energy required to re-form bonds in product molecules

[Done] Which describes an atom that has fewer neutrons than protons and more electrons than protons? A. negative compound B. positive compound C. positive ion D. negative ion

[Done] 1. How are solids, liquids, and gases similar? 2. Why do you think matter needs to change from one state to another in everyday life? Can you give me an example? 3. Which state of matter do you think is the most important for life? Justify your answer with examples.