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3 years ago

How many half-lives will pass by the time 1.56% of I-131 is present? B. Approximately how many days does that equal? *

Chemistry

1 answer:

serg [7]3 years ago

6 0

Answer: Hmmmmm that's crazy....

There are a couple of equations one could use for this type of problem, but I find the following to be the easiest to use and to understand.

Fraction remaining (FR) = 0.5n

n = number of half lives that have elapsed

In this problem, we need to find n and are given the FR, which is 1.56% or 0.0156 (as a fraction).

0.0156 = 0.5n

log 0.0156 = n log 0.5

-1.81 = -0.301 n

n = 6.0 half lives have elapsed

Explanation:

Just wanted to help. Hopefully it's correct wouldn't want to waster your time ;)

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Aspirin sun thesis Green Chemistry and Assime the aspirin is prepared by the following reaction and that 10.09. of salicylic aci

klemol [59]

Answer: The percentage yield of aspirin is 38.02 %.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ .....(1)

For salicylic acid:

Given mass of salicylic acid $(C_7H_6O_3)$ = 10.09 g

Molar mass of salicylic acid $(C_7H_6O_3)$ = 138.12 g/mol

Putting values in equation 1, we get:

$\text{Moles of salicylic acid}=\frac{10.09g}{138.12g/mol}=0.0730mol$

The chemical equation for the formation of aspirin follows:

$C_7H_6O_3+C_4H_6O_3\rightarrow C_9H_8O_4+CH_3COOH$

As, acetic anhydride is present in excess. So, it is considered as an excess reagent.

Thus, salicylic acid is a limiting reagent because it limits the formation of products.

By Stoichiometry of the reaction:

1 mole of salicylic acid produces 1 mole of aspirin.

So, 0.0730 moles of salicylic acid will produce = $\frac{1}{1}\times 0.0730=0.0730mol$ of aspirin

Now, calculating the mass of aspirin from equation 1, we get:

Molar mass of aspirin = 180.16 g/mol

Moles of aspirin = 0.073 moles

Putting values in equation 1, we get:

$0.073mol=\frac{\text{Mass of aspirin}}{180.16g/mol}\\\\\text{Mass of aspirin}=13.15g$

To calculate the percentage yield of aspirin, we use the equation:

$\%\text{ yield}=\frac{\text{Experimental yield}}{\text{Theoretical yield}}\times 100$

Experimental yield of aspirin = 5.0 g

Theoretical yield of aspirin = 13.15 g

Putting values in above equation, we get:

$\%\text{ yield of aspirin}=\frac{5.0g}{13.15g}\times 100\\\\\% \text{yield of aspirin}=38.02\%$

Hence, the percent yield of aspirin is 38.01 %.

6 0

3 years ago

Calculate the percentage by mass of the indicated element in the following compounds. Hydrogen in ascorbic acid, HC6H7O6, also k

Scorpion4ik [409]

Answer: The mass percent of hydrogen in ascorbic acid is 4.5 %

Explanation:

In $C_6H_8O_6$ , there are 6 carbon atoms, 8 hydrogen atoms and 6 oxygen atoms.

To calculate the mass percent of element in a given compound, we use the formula:

$\text{Mass percent of hydrogen}=\frac{\text{Mass of hydrogen}}{\text{Molar mass of ascorbic acid}}\times 100$

Mass of hydrogen = $8\times 1g/mol=8g$

Molar Mass of ascorbic acid = $6\times 12g/mol+8\times 1g/mol+6\times 16g/mol=176g$

Putting values in above equation, we get:

$\text{Mass percent of hydrogen}=\frac{8g}{176}\times 100=4.5\%$

Hence, the mass percent of of hydrogen in ascorbic acid is 4.5 %.

8 0

3 years ago

What is the number of grams of an element that is numerically equal to the atomic mass in amu?

bagirrra123 [75]

The wording of your question doesn't quite make sense, but a mole of an element has the same mass in grams as a single atom of that element has in amu. The mole is defined as 6.02 x10^22 things, whether they be atoms or molecules or even moles! 6.02x10^22 atoms of carbon has a mass of 12.01 g, and a single atom of carbon has a mass of 12.01 amu. Hope this helps!

3 0

3 years ago

Isoelectric point. The isoelectric point (pI) is the pH at which a molecule has no net charge. The amino acid glycine has two io

timama [110]

Answer:

pI = 6.16

Explanation:

The pI is given by the average of the pKas that are involved. In this case,

Pka of carboxylic acid was given as 2.72 and that of the Amino group was given as 9.60. the average would then be ½(2.72+9.60)

= 6.16

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3 years ago

What is the balanced equation for tin dioxide + hydrogen ---> tin +water

Nesterboy [21]

SnO2 + 2H2 >>> Sn + 2H2O

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3 years ago