Chemistry, 13.08.2020 19:01 DnsMonsteR3462

If a sample of C-14 initially contains 1.6 mmol of C-14, how many millimoles will be left after 2250 years

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Answer from: aaminohasan142

1.2 millimoles will be left after 2250 years

Explanation:

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 = age of sample

a = let initial amount of the reactant

a - x = amount left after decay process

a) for completion of half life:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

$t_{\frac{1}{2}}=\frac{0.693}{k}$

$k=\frac{0.693}{5730}=0.00012years^{-1}$

b) Amount left after 2250 years

$2250=\frac{2.303}{k}\log\frac{1.6}{a-x}$

$2250=\frac{2.303}{0.00012}\log\frac{1.6}{a-x}$

$\log\frac{1.6}{a-x}=0.117$

$\frac{1.6}{a-x}=1.31$

${a-x}=\frac{1.6}{1.31}=1.2$

Thus 1.2 millimoles will be left after 2250 years

Answer from: Quest

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.

Answer from: Quest

For cyclohexane compounds drawn in a chair conformation: -axial bonds are vertical -equatorial bonds are parallel to two bonds within the ring. thus, as i assume the chair conformation is drawn: -the x group is in an axial position, as are the five other vertical bonds. -three axial bonds are on the top face of the ring -the other three axial bonds are on the bottom face the position of the second substituent on each ring carbon is equatorial. gauche groups must be on an adjacent carbon such as carbon 6 and carbon 2, and also gauche groups are rotated by 60 degrees relative to each other. drawing the newman projections for c1–c2 and c1–c6 aids in visualizing the groups that are gauche to the y group on c1. click this link and watch some academic videos that may you more understand the topic

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If a sample of C-14 initially contains 1.6 mmol of C-14, how many millimoles will be left after 2250...

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