Which of the following does not show a correct relationship between units? a. 10

Question

Which of the following does not show a correct relationship between units? a. 1000 grams = 1 kilogram b. 1 gigabyte = 1 times 10^9 bytes c. 1 nanometer = 1 times 10^-9 meters d. 1 times 10^-6 micro liters = 1 liters = 1 liter e. 1 times 10^-3 second = 1 millisecond According to the law of definite proportions, _ a. different samples of the same compound contain the same proportions of the same elements. b. atoms forming, given compound react in viable proportions depending on conditions. c. all compounds containing the same types of atoms have identical properties. d. all compounds containing the same types of atoms have relative masses that are whole-number multiples. e. only one type of molecule can be produced when two elements combine. Which of the following statements is NOT true? a. A compound always contains the same mass percentages of its constituent elements. b. A large sample and a small sample of a given compound contain the same number of each type of atom. c. A large sample and a small sample of a compound share the same chemical formula. d. A large sample and a small sample of a given compound contain the same types of atoms combined in the same proportions. e. The relative numbers of each type of atom in a given compound do not vary. What is the formula for the ionic compound formed when calcium and bromine combine? a. CaBrO b. Ca2Br c. CaB, d. CBr e. CaBr_2 A particular brand of beer must maintain an alcohol content by volume of 5 65 to 5.75%. Analyses at four independent labs of an artificial beer sample with an alcohol content of 5.68% by volume yielded the following data. What can be deduced from these results? a. The data from lab 4 should be used based on its precision. b. The values from lab 1 are both imprecise and inaccurate. c. Lab 2 provides sufficiently precise and accurate values. d. The values from lab 3 are sufficiently precise and accurate. e. None of the data meet the brewers specifications.

Explanation / Answer

7) (a) 1 kg = 1000 g; hence (a) is correct.

(b) 1 gigabyte = 1*109 bytes; the relationship is correct.

(c) 1 nanometer = 1*10-9 m; the relationship is correct.

(d) 1*10-6 microliters = (1*10-6 microliters)*(1 liter/106 microliters) = 1*10-12 liters (since 1 L = 1*106 microliters); hence the relationship is wrong.

(e) 1*10-3 second = (1*10-3 second)*(1000 millisecond/1 second) = 1 millisecond (since 1 second = 1000 millisecond); hence the relationship is correct.

Ans: (d)

8) The law of definite proportions states that no matter what the source of a compound, a compound will always contain its constituent atoms in the same fixed proportion. Option (a) conveys the same idea and is the correct answer.

Ans: (a)

9) The mass percentages of the constituent elements remain the same in a compound no matter how the compound was prepared. For example, CO2 will always contain 27.27% C and 72.73% O, no matter from where we obtain the sample of CO2.

The same compound will always contain the same constituent atoms combined in the same fixed proportion and will always have the same chemical properties. Therefore, all the points except (b) are correct. This is because, the larger the size of the sample, the greater is the number of moles of the compound and hence greater will be the number of molecules. Since molecules are composed of atoms, this automatically means that the number of atoms will be higher in a large sample.

Ans: (b)

10) Ca ionizes in aqueous solutions to give dipostively charged Ca2+ ions. Bromine ionizes in aqueous solution to give mononegative Br- ions. The positive and negative ions combine in 1:2 ratio (cation:anion) to balance the charges; hence the formula of the compound is CaBr2.

Ans: (e)

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