# Solved > 61) How many half-lives are required for the:1936547 …

61) How many half-lives are required for the concentration of reactant to decrease to 12.5% of its original value?

A) 3

B) 1

C) 1.75

D) 2.75

E) 2

62) How many half-lives are required for the concentration of reactant to decrease to 1.56% of its original value?

A) 6

B) 5

C) 7

D) 6.5

E) 7.5

63) If the concentration of a reactant is 6.25%, how many half-lives has it gone through?

A) 7

B) 6

C) 3

D) 4

E) 5

64) The rate constant for the first-order decomposition of N2O is 3.40 s-1. What is the half-life of the decomposition?

A) 0.491 s

B) 0.204 s

C) 0.236 s

D) 0.424 s

E) 0.294 s

65) The half-life for the second-order decomposition of HI is 15.4 s when the initial concentration of HI is 0.67 mol L-1. What is the rate constant for this reaction?

A) 1.0 × 10-2 L mol-1 s-1

B) 4.5 × 10-2 L mol-1 s-1

C) 9.7 × 10-2 L mol-1 s-1

D) 2.2 × 10-2 L mol-1 s-1

E) 3.8 × 10-2 L mol-1 s-1

66) The rate constant for a second-order reaction is 0.54 L mol-1 s-1. What is the half-life of this reaction if the initial concentration is 0.27 mol L-1?

A) 2.0 s

B) 5.0 s

C) 0.25 s

D) 6.9 s

E) 1.3 s

67) The rate constant for a first-order reaction is 0.54 L mol-1 s-1. What is the half-life of this reaction if the initial concentration is 0.27 mol L-1?

A) 2.0 s

B) 5.0 s

C) 0.25 s

D) 6.9 s

E) 1.3 s

68) The rate constant for a zero-order reaction is 0.54 L mol-1 s-1. What is the half-life of this reaction if the initial concentration is 0.27 mol L-1?

A) 2.0 s

B) 5.0 s

C) 0.25 s

D) 6.9 s

E) 1.3 s

69) The half-life for the decay of radium is 1620 years. What is the rate constant for this first-order process?

A) 4.28 × 10-4 yr-1

B) 1.12 × 10-4 yr-1

C) 2.33 × 10-4 yr-1

D) 8.91 × 10-4 yr-1

E) 6.17 × 10-4 yr-1

70) The first-order decomposition of cyclopropane has a rate constant of 6.7 × 10-4 s-1. If the initial concentration of cyclopropane is 1.33 mol L-1, what is the concentration of cyclopropane after 644 s?

A) 0.43 mol L-1

B) 0.15 mol L-1

C) 0.94 mol L-1

D) 0.86 mol L-1

E) 0.67 mol L-1

GraduateWriterHelp.com is an online academic writing platform that provides extensive assistance to graduate school students as they work through their research projects, papers and dissertations. GraduateWriterHelp.com gives students access to experienced professionals who can provide the help they need in a timely and efficient manner. The service offers a wide range of services, including editing, proofreading, formatting, researching and more that can give students the confidence they need to write the perfect paper or dissertation for their chosen subject matter.

GraduateWriterHelp.com offers a wealth of different services designed to make research projects easier for graduate school students. These include editing, proofreading, formatting and researching services, all tailored specifically for graduate-level studies such as PhDs or Master’s degrees in any field from business administration to engineering or even psychology – all with the aim of helping busy students find success in their academics without having to sacrifice other important commitments like family time or work hours towards earning a living wage outside of college hours.

This service allows users only pay for what students need, which tends to be much lower overall because customers pay per hour rather than project basis, thus resulting to greater financial flexibility, especially for those just starting out postgraduate studies looking to conserve some pennies here there whenever possible!

## Calculate the price of your order

550 words
We'll send you the first draft for approval by September 11, 2018 at 10:52 AM
Total price:
\$26
The price is based on these factors:
Number of pages
Urgency
Basic features
• Free title page and bibliography
• Unlimited revisions
• Plagiarism-free guarantee
• Money-back guarantee
On-demand options
• Writer’s samples
• Part-by-part delivery
• Overnight delivery
• Copies of used sources
Paper format
• 275 words per page
• 12 pt Arial/Times New Roman
• Double line spacing
• Any citation style (APA, MLA, Chicago/Turabian, Harvard)

# Our guarantees

Delivering a high-quality product at a reasonable price is not enough anymore.
That’s why we have developed 5 beneficial guarantees that will make your experience with our service enjoyable, easy, and safe.

### Money-back guarantee

You have to be 100% sure of the quality of your product to give a money-back guarantee. This describes us perfectly. Make sure that this guarantee is totally transparent.

### Zero-plagiarism guarantee

Each paper is composed from scratch, according to your instructions. It is then checked by our plagiarism-detection software. There is no gap where plagiarism could squeeze in.

### Free-revision policy

Thanks to our free revisions, there is no way for you to be unsatisfied. We will work on your paper until you are completely happy with the result.