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3 years ago

A collection of coins contains 15 pennies, 14 dimes and 6 quarters. What is the percentage of pennies in the collection?

Chemistry

1 answer:

pychu [463]3 years ago

8 0

Answer:

42.9%

Explanation:

the total number of coins is 15+14+6 = 35

so to find the % of pennies, divide the number of pennies by the total number of coins and times it all by 100

15/35 x 100 = 42.9%

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The reaction will generally form more reactants than products.

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A helium filled ballon had a volume of 8.50 L on the ground at 20.0 C and a pressure of 750.0 Torr. After the ballon was release

Marrrta [24]

Answer:

$V_2=12.1L$

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3 years ago

A wooden artifact from a Chinese temple has a 14C activity of 42.8 counts per minute as compared with an activity of 58.2 counts

Arlecino [84]

Answer : The age of the artifact is, $2.54\times 10^3\text{ years}$

Explanation :

Half-life = 5715 years

First we have to calculate the rate constant, we use the formula :

$k=\frac{0.693}{5715\text{ years}}$

$k=1.21\times 10^{-4}\text{ years}^{-1}$

Now we have to calculate the time taken to decay.

Expression for rate law for first order kinetics is given by:

$t=\frac{2.303}{k}\log\frac{a}{a-x}$

where,

k = rate constant

t = time taken by sample = ?

a = initial activity of the reactant = 58.2 counts per minute

a - x = activity left after decay process = 42.8 counts per minute

Now put all the given values in above equation, we get

$t=\frac{2.303}{1.21\times 10^{-4}}\log\frac{58.2}{42.8}$

$t=2540.5\text{ years}=2.54\times 10^3\text{ years}$

Therefore, the age of the artifact is, $2.54\times 10^3\text{ years}$

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3 years ago

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