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2 years ago

After 42 days, a 2.0 g sample of phosphorous-32 contains only 0.25 g of the isotope. What is the half-life of phosphorus-32?

Chemistry

1 answer:

tester [92]2 years ago

4 0

Answer:

Half life of phosphorous-32 = 14 days

Explanation:

Given data:

Total mass of phosphorous-32 = 2.0 g

After 42 days mass left = 0.25 g

Half life of phosphorous-32 = ?

Solution:

First of all we will calculate the number of half lives passed.

At time zero = 2.0 g

At first half life = 2.0 g/2 = 1.0 g

At 2nd half life = 1.0 g/2 = 0.5 g

At 3rd half life = 0.5 g/2 = 0.25 g

Half life:

Half life = T elapsed / half lives

Half life = 42 days/ 3

Half life = 14 days

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2 years ago

199.5 grams unrefined dark crystalline sugar to cups

Dmitry [639]

Answer:

0.9975 cup

Step-by-step explanation:

"Unrefined dark crystalline sugar" is what non-chemists call "brown sugar."

200.0 g brown sugar = 1 cup

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199.5 g brown sugar = 0.9975 cup

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3 years ago

What is the theoretical yield of fluorenone if you oxidize 175 mg of fluorene?

My name is Ann [436]

Answer:

602 mg of CO₂ and 94.8 mg of H₂O

Explanation:

The yield is measured by the amount of each product produced by the reaction.

The chemical formula of fluorene is C₁₃H₁₀, and its molar mass is 166.223 g/mol.

The oxidation, also know as combustion, of this hydrocarbon is represented by the following balanced chemical equation:

$2C_{13}H_{10}+31O_2\rightarrow 26CO_2+10H_2O$

To calculate the yield follow these steps:

1. Mole ratio

$2molC_{13}H_{10}:31molO_2:26molCO_2:10molH_2O$

2. Convert 175mg of fluorene to number of moles

$175mg/times 1g/1,000mg=0.175g$

Number of moles = mass in grams / molar mass

$\text{number of moles}=0.175g/166.223g/mol=0.0010528mol$

3. Set a proportion for each product of the reaction

a) For CO₂

i) number of moles

$2molC_{10}H_{13}/26molCO_2=0.0010528molC_{10}H{13}/x$

$x=0.0010528molC_{10}H_{13}\times 26molCO_2/2molC_{10}H_{13}=0.013686molCO_2$

ii) mass in grams

The molar mass of CO₂ is 44.01g/mol

mass = number of moles × molar mass

mass = 0.013686 moles × 44.01 g/mol = 0.602 g = 602mg

b) For H₂O

i) number of moles

$0.0010528molC_{10}H_{13}\times10molH_2O/2molC_{10}H_{13}=0.00526molH_2O$

ii) mass in grams

The molar mass of H₂O is 18.015g/mol

mass = number of moles × molar mass

mass = 0.00526 moles × 18.015 g/mol = 0.0948mg = 94.8 mg

4 0

3 years ago

Water temperature is general cooler where?

Arada [10]

The temperature of water is cooler in deep oceans. The temperature there goes to 0°C to -3°C below which the water freezes. The water on the surface of the oceans and deep inside it varies because of the difference in energy of the two layers. One of the widest use of cold water is air conditioning. Cold water has a higher density than warm water. Water gets colder with profundity since chilly, salty sea water sinks to the base of the sea beds underneath the less dense hotter water close to the surface.

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3 years ago

How many atoms are in 26.8 g Fe

Tatiana [17]

Answer:

2.881x10^23 atoms

Explanation:

From the studies of Avogadro's hypothesis, we discovered that 1mole of any substance contains 6.02x10^23 atoms.

Therefore 1mole of Fe contains 6.02x10^23 atoms.

Molar Mass of Fe = 56g/mol

56g of Fe contains 6.02x10^23 atoms.

Therefore, 26.8g of Fe will contain = (26.8x6.02x10^23) / 56 = 2.881x10^23 atoms

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3 years ago