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vlabodo [156]
3 years ago
15

Carbon-14 has a half-life of 5720 years and this is a first order reaction. If a piece of wood has converted 75% of the carbon-1

4, how old is it?
A. 11440 years
B. 2345 years
C. 4750 years
D. 4290 years
E. 1430 years
Chemistry
1 answer:
shutvik [7]3 years ago
7 0
The answer will be the first option, i.e. 11440 years since the piece of wood has undergone two half lives
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Which of the following is true for an excess reactant?
kupik [55]

Answer:

C) It is the reactant that is left over after the reaction stops.

Explanation:

The excess reactant is the reactant that is left over after the reaction stops. The extent of the reaction is not determined by this reactant.

A limiting reactant is a reactant that is in short supply within a given reaction.

Such reactants determines the extent of chemical reaction.

  • Limiting reactants are used up in a chemical reaction.
  • The excess reactants remains unchanged after the reaction.
8 0
2 years ago
A fossil was analyzed and determined to have a carbon-14 level that is 70 % that of living organisms. The half-life of C-14 is 5
Citrus2011 [14]

Answer: 2948

Explanation:

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{0.69}{t_{\frac{1}{2}}}=\frac{0.693}{5730}=1.21\times 10^{-4}years^{-1}

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  = 1.21\times 10^{-4}years^{-1}

t = age of sample  = ?

a = let initial amount of the reactant  = 100

a - x = amount left after decay process = \frac{70}{100}\times 100=70

t=\frac{2.303}{1.21\times 10^{-4}}\log\frac{100}{70}

t=2948years

Thus the fossil is 2948 years old.

5 0
2 years ago
Does a chemical bond join atoms together in a water molecule?
MrRissso [65]
Yes. 

A covalent bond holds it together, which is chemical. 
3 0
2 years ago
Timed PLS help
Bezzdna [24]

Answer:

19.5g is the theoretical yield of alum

Explanation:

Based on the balanced reaction, 4 moles of sulfuric acid produce 2 moles of alum. To solve this question we need to find the moles of H2SO4. With these moles we can find the moles of alum and its mass assuming all sulfuric acid reacts producing alum.

<em>Moles Sulfuric Acid:</em>

8.3mL = 0.0083L * (9.9mol/L) = 0.08217 moles sulfuric acid

<em>Moles Alum:</em>

0.08217 moles sulfuric acid * (2mol KAl(SO4)2•12H2O / 4mol H2SO4) =

0.041085 moles KAl(SO4)2•12H2O

<em>Mass Alum -Molar mass: 474.3884 g/mol-</em>

0.041085 moles KAl(SO4)2•12H2O * (474.3884 g/mol) =

<h3>19.5g is the theoretical yield of alum</h3>
3 0
2 years ago
The first-order decomposition of cyclopropane has a rate constant of 6.7 x 10-4 s-1. if the initial concentration of cyclopropan
vaieri [72.5K]
The first order rate law has the form: -d[A]/dt = k[A] where, A refers to cyclopropane. We integrate this expression in order to arrive at an equation that expresses concentration as a function of time. After integration, the first order rate equation becomes:

ln [A] = -kt + ln [A]_o, where,

k is the rate constant
t is the time of the reaction
[A] is the concentration of the species at the given time
[A]_o is the initial concentration of the species

For this problem, we simply substitute the known values to the equation as in:

ln[A] = -(6.7 x 10⁻⁴ s⁻¹)(644 s) + ln (1.33 M) 

We then determine that the final concentration of cyclopropane after 644 s is 0.86 M.
5 0
3 years ago
Read 2 more answers
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