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hoa [83]
2 years ago
6

In order to understand the prehistory of the Hawaiian island of Lana'i better, anthropologists Maria Sweeney, Melinda Allen, and

Boyd Dixon used radiocarbon dating on charcoal found in an ancient dwelling site, the Kaunolu Village National Historic Landmark, the largest archeological complex on the island. In one of their samples, they found that approximately 94% of the original carbon 14 remained. Using the fact that Carbon 14 decays by 1.202% every 100 years, determine the approximate age of this sample.
Chemistry
1 answer:
AleksandrR [38]2 years ago
4 0

Answer:

500 years

Explanation:

The original carbon-14 was 100%, and after 100 years, it decays 1.202%. So after 100 years it goes to 98.798%, after more 100 years (200 years), it will be 97.596% (98.798 - 1.202), thus, after n 100 years "package", the percenatge will be:

100% - actual% = n*1.202

n = (100% - actual%)/1.202

n = (100% - 94%)/1.202

n = 4.992

So, the number of years is n*100 = 4.992*100 = 499.2 ≅ 500 years.

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When 1.98g of a hydrocarbon is burned in a bomb calorimeter, the temperature increases by 2.06∘C. If the heat capacity of the ca
schepotkina [342]

Answer:

8.3 kJ

Explanation:

In this problem we have to consider that both water and the calorimeter absorb the heat of combustion, so we will calculate them:

q for water:

q H₂O = m x c x ΔT where m: mass of water = 944 mL x 1 g/mL = 944 g

                                      c: specific heat of water = 4.186 J/gºC

                                     ΔT : change in temperature = 2.06 ºC

so solving for q :

q H₂O = 944 g x 4.186 J/gºC x 2.06 ºC = 8,140 J

For calorimeter

q calorimeter  = C x  ΔT  where C: heat capacity of calorimeter = 69.6 ºC

                                     ΔT : change in temperature = 2.06 ºC

q calorimeter = 69.60J x 2.06 ºC = 143.4 J

Total heat released = 8,140 J +  143.4 J = 8,2836 J

Converting into kilojoules by dividing by 1000 we will have answered the question:

8,2836 J x 1 kJ/J = 8.3 kJ

7 0
3 years ago
ch question carries 2 mark. Time Remaining : 00 : 46 : 33 Some oxides are given below. (i)Na2O (ii)NO2 (iii) CO2 (iv) MgO a) Whi
cluponka [151]
<h3>Further explanation</h3>

The basic oxide is an oxide-forming a base solution.

These oxides are mainly from group 1 alkaline and group 2-alkaline earth

If this oxide is dissolved in water it will form an alkaline solution

LO + H₂O --> L(OH)₂ ---> alkaline earth

L₂O + H₂O --> LOH --> alkaline

So the basic oxides  : Na₂O and MgO

Na₂O + H₂O --> NaOH (sodium hydroxide, strong base)

MgO + H₂O --> Mg(OH)₂ (magnesium hydroxide, strong base)

The aqueous solution of CO₂ , obtained by dissolving CO₂ in water

CO₂ + H₂O --> H₂CO₃ (carbonic acid)

In general, basic oxide is obtained from metal oxide, while acid oxide is obtained from non-metal oxide

6 0
3 years ago
In the combustion chamber of an engine, the initial volume is 450 cm3 at a pressure of 1.0 atmosphere. If the piston displaces 4
Alona [7]

Assuming that the contents of the chamber ar ideal gases. We can use the relation PV=nRT.  At a constant temperature and number of moles of the gas the product of PV is equal to some constant. At another set of condition of temperature, the constant is still the same. Calculations are as follows:

 

P1V1 =P2V2

P2 = (1)(450)/ 48

P2 = 9.375 atm

3 0
3 years ago
Use the molar heat capacity for aluminum from table 1 to calculate the amount of energy needed to raise the temperature of 260.5
Nimfa-mama [501]
Unfortunately, you failed to include the table 1 from which the molar heat capacity of aluminum could have been obtained. However, as a general rule, the heat needed to raise the temperature of a certain substance by certain degrees is calculated through the equation,
                            H = mcpdT
where H is heat, m is mass, cp is specific heat capacity, and dT is change in temperature. From a reliable source, cp for aluminum is equal to 0.215 cal/g°C. Substituting this to the equation,
                               H = (260.5 g)(0.215 cal/g°C)(125°C - 0)
                                        H = 7000.94 cal
6 0
3 years ago
How many moles of zinc are needed to react with 45.60 moles of nitric acid?
uranmaximum [27]

Answer:

11.4 moles

Explanation:

Your chemical equation for the reaction of zinc and nitric acid will be

Zn  +  4 HNO₃  -->  Zn(NO₃)₂  +  2 NO₂  +  2 H₂O

To solve the problem, you need to use stoichiometry.  For every 1 mole of zinc, you will need 4 moles of nitric acid.  Divide 45.60 by 4.  Your answer should be 11.4 moles.

3 0
3 years ago
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