Radioactive decay => C = Co { e ^ (- kt) |
Data:
Co = 2.00 mg
C = 0.25 mg
t = 4 hr 39 min
Time conversion: 4 hr 39 min = 4.65 hr
1) Replace the data in the equation to find k
C = Co { e ^ (-kt) } => C / Co = e ^ (-kt) => -kt = ln { C / Co} => kt = ln {Co / C}
=> k = ln {Co / C} / t = ln {2.00mg / 0.25mg} / 4.65 hr = 0.44719
2) Use C / Co = 1/2 to find the hallf-life
C / Co = e ^ (-kt) => -kt = ln (C / Co)
=> -kt = ln (1/2) => kt = ln(2) => t = ln (2) / k
t = ln(2) / 0.44719 = 1.55 hr.
Answer: 1.55 hr
Answer: 
: Pure substance, Element
: Pure substance , Element
: Pure substance, Compound
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: 
and
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example:
Heterogeneous Mixture : Mixture that has its different components mixed unevenly within the substance
. Example: Air
Homogeneous Mixture : Mixture that has its different components mixed evenly within the substance. Example: sugar dissolved in water
The answers are A. Pseudoscience is often based only on opinions; D. Pseudoscience often involves explanations of beliefs; E. Pseudoscience includes subjective ideas.
Explanation:
Pseudosciences comprises disciplines or theories that do not follow scientific standards but claim to be factual. This includes areas such as clairvoyance or astrology because this is not based on evidence but subjectivity. Indeed, the base of most pseudosciences are personal beliefs, opinions, or subjective ideas. Moreover, complex theories or methods are created to try to explain these beliefs, but because they do not follow scientific standards they are not considered as valid. In this context, options A, D, and E are correct.
Answer:
Fossils are the some traces or portions of the animals or plants, buried and preserved from past in rocks, sediments or ice.
Explanation:
Correct match is as follows-
- Mold and cast fossils- An organism is buried in sediment after it dies.The hard part of organism leave behind a empty space imprinted in the rock. Later sediments and minerals fill the space and harden to make the original copy of the organisms.
- Carbon film fossils- An organism buried in sediments gets squeezed and heated inside the earth , leaving behind a thin carbon outline of the organism on a rock.
- Amber fossil- An organism covered in tree resin or tree sap , which then hardens with the body of the organisms preserved inside.
- Ice fossil- An organism dies in a cold place on earth , its body becomes frozen and covered in layers of ice . The hard and soft part of the body may be preserved.
