Question

a. the atomic mass is calculated by adding the masses of protons to neutrons, and protons have greater mass than neutrons. b. the atomic mass can only be determined when the mass of protons, neutrons, and electrons are taken into consideration. c. the atomic mass is calculated by averaging the mass of one atom of each isotope that exists. d. the atomic mass is weighted average mass of the isotopes of an atom, based on how common each isotope is. 25. a radioactive isotope of an element is used frequently in medical diagnosis. this isotope has an atomic number of 43 and a mass number of 99. which description would represent the number of subatomic particles of this particle? a. 43 protons, 56 neutrons, and 43 electrons b. 43 protons, 43 neutrons, and 56 electrons c. 99 protons, 43 neutrons, and 99 electrons d. 43 protons, 56 neutrons, and 56 electrons 26. which of the following substances are considered a homogenous mixture? a. an animal cell b. air c. sugar d. oil & vinegar salad dressing 27. a curious and bored student (well call him george) wants to know how long it would take to count to 1 million if he counted a number each second. so how many weeks is 1,000,000 seconds? (answers are shown to 4 sigfigs.) a. 99.21 weeks b. 11.57 weeks c. 1.653 weeks d. 3.307 weeks 28. a curious and bored student (george again) wants to see how fast he can run a mile around his neighborhood. he only has a tape measure that measures inches. how many inches will he have to measure out to get 1 mile? (answers are shown to 4 sigfigs.) a. 63360 inches b. 5280 inches c. 12000 inches d. 24940 inches 29. in chemistry, substances are generally classified as either a pure substance or a mixture. which choice has the terms grouped properly with their classification? classifications: mixture & pure substance terms: compound, element, heterogeneous, & homogenous

Explanation:

Step1: Determine sub - atomic particles for 25

The atomic number is the number of protons. Mass number = protons + neutrons. Given atomic number 43 and mass number 99, neutrons = 99 - 43=56. In a neutral atom, number of electrons = number of protons.

Step2: Identify homogeneous mixture for 26

Air is a homogeneous mixture of gases. An animal cell is a living entity, sugar is a pure substance, and oil & vinegar salad dressing is a heterogeneous mixture.

Step3: Convert seconds to weeks for 27

There are 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day and 7 days in a week. So, 1000000 seconds $\times\frac{1\ minute}{60\ seconds}\times\frac{1\ hour}{60\ minutes}\times\frac{1\ day}{24\ hours}\times\frac{1\ week}{7\ days}\approx11.57$ weeks.

Step4: Convert miles to inches for 28

1 mile = 5280 feet and 1 foot = 12 inches. So, 1 mile = 5280×12 = 63360 inches.

Step5: Classify substances for 29

Elements and compounds are pure substances as they have a definite composition. Heterogeneous and homogenous are terms used to describe mixtures.

Answer:

1. B. 43 protons, 56 neutrons, and 43 electrons
2. B. air
3. B. 11.57 weeks
4. A. 63360 inches
5. Compounds and elements are pure substances; heterogeneous and homogenous are types of mixtures.