The half-life of Th-232 is 1.405 × 10¹⁰ years
Time elapsed = 2.8 x 10⁹ years
Equation of radioactive decay:
A = A₀ = (1/2)^ t/t₁/₂
where A₀ is the initial amount, A is the amount after time t, t₁/₂ is the half file
The fraction of thorium-232 that remains in the rock after 2.8 billions years is,
A/A₀ = (1/2) ^ (2.8 x 10⁹/ 1.405 × 10¹⁰) = 0.871
Therefore, the percentage of thorium-232 in the rock that was dated at 2.8 billions year = 87.1%
Answer:
The answer I would go with is A formation of a new substance.
Explanation:
This is because physical change includes changes of state. Some could be changing from a liquid to gas or solid to gas. B is not even an answer that should be considered because it doesn't fit into the category. C and D represents some of the examples of the process of physical change. Like boiling, bubbling, melting, or freezing. So the best would be A.
Complete Question
The complete question is shown on the first uploaded image
Answer:
The consumption of the reactant benzophenone and the production of triphenylmethanol can be detected using their IR absorption spectrum
This reaction is shown on the second uploaded image
The reactant benzophenone is a compound which contains a carbonyl functional group, and the stretching frequency of C=O bond has a high absorption at around 
and frequency band of this wavelength is absent in triphenylmethanol.
in the same vain the product triphenylmethanol is a compound which contains a hydroxyl (OH) functional group, and the stretching frequency of O-H bond has a high absorption at around 
and frequency band of this wavelength is absent in benzophenone.
To use infrared spectroscopy to show that the reaction is occurring is to show the disappearance of the frequency band which indictes the consumption of benzophenone and the appearance frequency band which indictes the formation of triphenylmethanol
Explanation:
Answer: Limestone is a sedimentary rock.
Explanation:
1. Limestone is a carbonate sedimentary rock made up of calcite(CaCO₃).This rock type forms calcareous shells and tests of organisms that was deposited in a sedimentary basin.
Limestone is used in building and construction works. It also finds application in chemical industries.
2. Over a long period of time, we would take a look at the rock "limestone" through the rock cycle.
Limestone being a sedimentary rock would be converted to marble, a metamorphic rock if subjected to metamorphic conditions over an extensive period of time. With series of metamorphic transformation, marble can grade to higher metamorphic facies of rocks as it combines with other minerals in the crust. The minerals would eventually change and as the changed rock approaches its melting temperature, melt would result.
From the other spectrum, limestone can be weathered if subjected extensively to denudation forces such as wind, water and glaciation. Water is more potent for the chemical weathering of limestone. Limestone would easily and readily dissolve in it over a long period of time.
b) The reactivity of alkali metals increases as atomic mass increases.
