1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Novosadov [1.4K]
3 years ago
5

A first-order reaction has a half-life of 16.7 s . How long does it take for the concentration of the reactant in the reaction t

o fall to one-fourth of its initial value?
Chemistry
1 answer:
andrew11 [14]3 years ago
5 0

It takes 33.4 s for the concentration of A to fall to one-fourth of its original value.

A <em>half-life</em> is the time it takes for the concentration to fall to half its original value.

Assume the initial concentration is 1.00 mol/L. Then,

\text{1.00 mol/L }\stackrel{\text{1st half-life }}{\longrightarrow}\text{ 0.50 mol/L } \stackrel{\text{ 2nd half-life }}{\longrightarrow}\text{0.25 mol/L}\\

The concentration drops to one-fourth of its initial value in two half-lives.

∴ Time = 2 × 16.7 s = 33.4 s

You might be interested in
Look at the equation for the reaction for nitric oxide and oxygen. Do you think this is a single-step reaction or a multistep re
Sveta_85 [38]

Answer:

This is most likely a multi-stepped reaction.

Explanation:

From the collision theory, we know that it is super improbable for 3 different molecules (2 NO and 1 O2) to all hit each other at the perfect speed in the perfect position to make the products. From this, we can pretty confidently say that this is most likely a multi-stepped reaction.

Hope this helps! :)

4 0
3 years ago
Calculate the ph of a 0.021 m nacn solution. [ka(hcn) = 4.9  10–10]
ohaa [14]

<span>Answer is: pH of solution of sodium cyanide is 11.3.
Chemical reaction 1: NaCN(aq) → CN</span>⁻(aq) + Na⁺<span>(aq).
Chemical reaction 2: CN</span>⁻ + H₂O(l) ⇄ HCN(aq) + OH⁻<span>(aq).
c(NaCN) = c(CN</span>⁻<span>) = 0.021 M.
Ka(HCN) =  4.9·10</span>⁻¹⁰<span>.
Kb(CN</span>⁻) = 10⁻¹⁴ ÷ 4.9·10⁻¹⁰ = 2.04·10⁻⁵<span>.
Kb = [HCN] · [OH</span>⁻] / [CN⁻<span>].
[HCN] · [OH</span>⁻<span>] = x.
[CN</span>⁻<span>] = 0.021 M - x..
2.04·10</span>⁻⁵<span> = x² / (0.021 M - x).
Solve quadratic equation: x = [OH</span>⁻<span>] = 0.00198 M.
pOH = -log(0.00198 M) = 2.70.
pH = 14 - 2.70 = 11.3.</span>

4 0
3 years ago
If the strength of the magnetic field at B is 10 units, the strength of the magnetic field at A is _____.
Sergeeva-Olga [200]
The answer is 40 units.

8 0
3 years ago
Read 2 more answers
Please help me with this!!?
Natali5045456 [20]

Answer:

The last answer is right they get half of the mothers genes and half of the fathers genes.

3 0
3 years ago
Atoms that differ only in the number of neutrons are called:
Natali [406]
The answer is C. Isotopes.

Isotopes are defined as two substances that have the same number of protons and electrons, but a different number of neutrons, and therefore a different atomic mass. For example, carbon-12 and carbon-14 are isotopes of each other.

Hope this helps!
8 0
3 years ago
Read 2 more answers
Other questions:
  • The continents may not have drifted slowly into their present positions. True False
    10·2 answers
  • Consider this reaction mechanism: Step 1: Mo(CO)6→ Mo(CO)5 + CO Step 2: Mo(CO)5 + P(CH3)3→ Mo(CO)5P(CH3)3 Which of these is an i
    7·1 answer
  • What are the contents of a electron cloud?
    7·1 answer
  • What changes are observed on heat capacity ratio and output temperatures by increasing the specific heat capacity of both the fl
    7·1 answer
  • How many atoms are here in the following?
    10·1 answer
  • Which types of reactions would result in a change in temperature?
    11·1 answer
  • These four ELEMENTS were found in early earth and they make up all living things.
    9·2 answers
  • QUESTION 4
    5·1 answer
  • How many moles of copper are present in a sample that contains 4.55 x 10^24 atoms of copper
    6·1 answer
  • C. By examining the physical and chemical properties of evidence at a crime scene, investigators can
    14·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!