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A certain radioactive material has a half-life of 36 minutes. Starting with 10.00 grams of this material, how many grams will be left after 2 hours?

A) 1.00 grams
B) 1.5 × 10-4 grams
C) 3.33 grams
D) 0.25 gram

User Yanna
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2 Answers

4 votes

Answer: The correct answer is C) 3.33 grams

Explanation: 1/8 of the initial 10 grams is a little more than 1 gram, while 1/16 of 10 grams is a little more than 1/2 gram. The only answer that falls in that range is 1.00 gram. Use the integrated rate equation: ln(g0/gt) = kt, also ln(2) = kt1/2. Therefore k = (0.693)/36 min = 0.0193 min-1. In addition to the specific chemical properties that distinguish different chemical classifications, chemicals can exist in several phases. For the most part, the chemical classifications are independent of these bulk phase classifications; however, some more exotic phases are incompatible with certain chemical properties. A phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. Physical properties, such as density and refractive index tend to fall within values characteristic of the phase. The phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions.

Sometimes the distinction between phases can be continuous instead of having a discrete boundary' in this case the matter is considered to be in a supercritical state. When three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions.

The most familiar examples of phases are solids, liquids, and gases. Many substances exhibit multiple solid phases. For example, there are three phases of solid iron (alpha, gamma, and delta) that vary based on temperature and pressure. A principal difference between solid phases is the crystal structure, or arrangement, of the atoms. Another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution (that is, in water).

User Bhargav Mistri
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3 votes
I think it's c hope it's right
User Petermolnar
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