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svetlana [45]
3 years ago
11

The half-life of C-14 is 5470 years. If a particular archaeological sample has one-quarter of its original radioactivity remaini

ng,what is the best estimate for its age?
Chemistry
1 answer:
Gennadij [26K]3 years ago
3 0

Answer:

When there remains one-quarter of the sample, the age of the sample is 10940 years

Explanation:

<u>Step 1:</u> Data given

The half-life of C-14 is 5470 years.

The half- life time is the time required for a quantity to reduce to half of its initial value.

This means after 5470 years there remains half of the C-14 sample.

To remain a quarter of the sample, another cycle of 5470 years is required.

This means 2 half-lives should have passed to remain a quarter of the sample.

<u>Step 2</u>: Calculate it's age

t/(t/1/2) = 2

⇒ with t = the age (or time) of the sample

⇒ with t(1/2) = the half-life time of the sample = 5470 years

⇒ with 2 = the number of halvf- lives passed

t/5470 = 2

t = 2*5470 = 10940 years

When there remains one-quarter of the sample, the age of the sample is 10940 years

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Answer:

It increases when a catalyst is added.

Explanation:

The following factors control reaction rates:

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2. Concentration of the reactants or pressure of gaseous

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4. Presence of catalyst

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The addition of a foreign body to a reaction may influence the speed of the reaction. If a foreign body increases the rate of reaction, it is a called a positive catalyst or simply a catalyst. A negative catalyst is called an inhibitor.

A catalyst is a substance that is introduced into a chemical reaction to change the rate of the reaction without itself being affected at the end of the reaction.

Catalysts helps to reduce reaction time of many slow reactions. Most catalysts are specific in their actions and works on certain reactions or substrates.

Temperature change has a considerable effect on reaction rates since temperature is directly proportional to the average kinetic energy of reacting particles. Generally, reaction rate varies as temperature directly.

8 0
3 years ago
The density of Mg is 1.74g/cm3. The density of strontium is 2.60g/cm3. What would you expect the density of Ca to be?
Tomtit [17]

The density of Ca will be between that of Mg and Sr

Explanation:

Ca, Mg and Sr are group II elements. They are called alkali earth metals. The correct order of the elements in this group are: Be, Mg, Ca, Sr, Ba and Ra.

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6 0
3 years ago
Chemical formula for 2 butyene is <br>​
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Explanation:

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Which mixture is classified as a solution?
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3 years ago
The Ostwald process is used commercially to produce nitric acid, which is, in turn, used in many modern chemical processes. In t
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Answer:

Mass =  42.8g

Explanation:

4 NH 3 ( g ) + 5 O 2 ( g ) ⟶ 4 NO ( g ) + 6 H 2 O ( g )

Observe that every 4 mole of ammonia requires 5 moles of oxygen to obtain 4 moles of Nitrogen oxide and 6 moles of water.

Step 1: Determine the balanced chemical equation for the chemical reaction.

The balanced chemical equation is already given.

Step 2: Convert all given information into moles (through the use of molar mass as a conversion factor).

Ammonia = 63.4g × 1mol / 17.031 g = 3.7226mol

Oxygen = 63.4g × 1mol / 32g = 1.9813mol

Step 3: Calculate the mole ratio from the given information. Compare the calculated ratio to the actual ratio.

If all of the 1.9831 moles of oxygen were to be used up, there would need to be 1.9831 × 4 / 5 or 1.5865 moles of Ammonia. We have 3.72226 moles of ammonia - Far excess. Because there is an excess of Ammonia, the Oxygen amount is used to calculate the amount of the products in the reaction.

Step 4: Use the amount of limiting reactant to calculate the amount of H2O produced.

5 moles of O2  = 6 moles of H2O

1.9831 moles = x

x = (1.9831 * 6 ) / 5

x = 2.37972 moles

Mass of H2O = Molar mass * Molar mass

Mass = 2.7972 * 18

Mass =  42.8g

6 0
3 years ago
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