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Natasha_Volkova [10]
2 years ago
9

Use Table 1: Analysis of Decay in the laboratory guide to answer this question: Scientists find a piece of wood that is thought

to be from an ancient fire circle. They find that the wood contains an amount of carbon-14 (14C) that is approximately 1/16 of the current atmospheric 14C levels. Determine approximately how many years ago the tree was chopped down to be used for the firewood. If you started with 1 million carbon-14 atoms, how many atoms would remain in the wood? 14C has a t1/2 of 5,750 years.
Why is 14C dating a good method to use for dating a human leg bone but not so good a method for dating a dinosaur bone? You may have to check the dates of the existence of humans and dinosaurs on earth on a chart showing the geological eras.
Potassium-40 (40K) is a radioactive material that decays into argon-40 (40Ar). The half-life of a sample of 40K is 1.3 billion years. Rocks containing 40K have been around since the formation of the earth, and 40Ar gas has been accumulating in those rocks since the earth formed. However, when rocks are heated by volcanic action, all the 40Ar leaves the rock when the gases escape. Create a scenario and discuss, based on your knowledge of half-life, the value of potassium-argon dating to geologists.
Chemistry
1 answer:
sashaice [31]2 years ago
8 0
1/2=5750 years, 1/2(1/2)=1/4, (1/2)(1/2)(1/2)=1/8, (1/2)(1/2)(1/2)(1/2)=1/6
4 halflives have passed so 4(5750)=23000 years since the tree was chopped down
1000000 atoms (1/2)=500000 atoms(1/2)=250000(1/2)=125000(1/2)=62500 atoms would remain in the wood after 4 halflives
Dinosaurs became extinct around 62 million years ago, so if 14C's half life has a value of 5750 years, it would be gone or in such small amounts that dating would be ineffective today.
As Potassium decays into Argon in 1.3 billion years, apart from volcanic activity, it would enable geologists to effectively date things that are really, really, really old. 
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If the volume of 425 grams was 48.0 cm³, simply divide

g/cm³ = 425 g/48 cm³ = 8.85 g/cm³

If using water in water displacement, 1 mL = 1 cm³

8.85 g/cm³ = 8.85 g/mL

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Hope I helped!
4 0
2 years ago
Tear gas has the composition 40.25% carbon, 6.19% hydrogen, 8.94% oxygen, 44.62% bromine. what is the empirical formula of this
andre [41]
<span>Calculating the moles and the moles ratio of the elements gives us the ratio of atoms in each element. Converting the percentage of element into grams 40.25% carbon = 40.25/100 = .4025 * 100 g of carbon = 40.25g of C 6.19% hydrogen = 6.19/100 = .0619 * 100g g of hydrogen = 6.19g of H 8.94% oxygen = 8.94/100 = .0819 * 100 g of oxygen = 8.19g of O 44.62% bromine = 44.62/100 = .4462 * 100 g of bromine = 44.62g of Br Converting the grams of element into moles (48.38 g C) (1 mol/ 12.10 g C) = 4.028 mol C (8.12 g H) (1 mol/ 1.008 g H) = 8.056 mol H (53.38 g O) (1 mol/ 16.00 g O) = 3.336 mol O (44.62g of Br)(0.012515018021626 moles) = 0.55842 mol Br Calculating the moles ratio of elements by dividing the small number of moles of an element 4.028 mol C /0.55842 = 7.2 mol C x 5 = 36 mol C 8.056 mol H / 0.55842 = 14.42 mol H = 72 mol H 3.336 mol O / 0.55842 = 5.97 mol O = 30 mol O 0.55842 mol Br / 0.55842 = 1mol Br = 5 mol Br So the empirical formula is (C6H12O5)6Br5</span>
8 0
2 years ago
Read 2 more answers
A metal sample is heated and placed into the water in a calorimeter at room temperature. Which statement best describes how the
andre [41]

Answer:

Energy transfers from the metal to the water and calorimeter until they are all at room temperature.

Explanation:

CHECK THE COMPLETE QUESTION BELOW;

A metal sample is heated and placed into the water in a calorimeter at room temperature. Which statement best describes how the calorimeter can be used to determine the specific heat capacity of the metal sample?

Energy transfers to the metal from the water and calorimeter until they are all at room temperature

. Energy transfers from the metal to the water and calorimeter until they are all at room temperature.

Energy transfers to the metal from the water and calorimeter until they all reach a single temperature.

Energy transfers from the metal to the water and calorimeter until they all reach a single temperature.

EXPLANATION;

Using calorimeter to determine the specific heat capacity of the metal sample can be associated to the theory of conservation of energy because heat which is a form of energy is been transfer of heat between the metal to the water and the calorimeter, this process will proceed till single temperature is attained.

The change in the amount of temperature of the water in the calorimeter is measured in order to get the difference in heat change of the calorimeter water.

CHANGE IN HEAT CAN BE CALCULATED USING THE FORMULA.

Q = cmΔT where Q is the change in heat , c is the specific heat capacity and ΔT is the change in temperature

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2 years ago
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this also happen when we lower the temperature
4 0
2 years ago
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MgBr2, 3 ions per mole=best conductor

KBr, 2 ions per mole, 2nd best conductor

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Sugar, molecular, non ionized, non conductor

8 0
2 years ago
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