General Chemistry Answers

What is the identity of an unknown given that its molar mass is 204.113 g/mol?

A. C₅H₁₀O₅

B. C₆H₆

C. P₂O₅

D. C₃N₁₂

What is the first step in solving for the empirical formula of an unknown compound?

A. Get the ratio of the elements

B. Calculate the number of moles

C. Calculate the percent composition

D. Look for the mole ratio

Calculate the mass of carbon dioxide, CO2, produced from 0.85 mole of sucrose, C₆H₁₂O₆, assuming that oxygen, O₂ is in excess.

A mole of a newly discovered crystalline substance weighs 14.56 grams and displaces 2.3 ml of water. What is the density of the crystal? Find the atomic radius and density of each atom if it is a simple cubic cell? BCC? FCC? HCP?

The following data is given:

t    10      20      30       40    

N  28.28  40    56.57   80

Which of the following numbers best describes the doubling time? (To answer the question you may draw a semi-log plot, i.e., plot logN against t, but may also be able to guess it by looking at the data.)

a) 10

b) -4

c) 20

d) 40

The half-life of Actinium-227 is 21.8 years. Suppose we have a 120-mg sample.

i. Which of the following is the function that describes how much is left after t years?

a) 21.8⋅2 ^ −(2 t /120)

b) 120⋅2 ^ −(t / 21.8)

c) 120⋅e ^ −(t / 21.8)

d) 120.t ^ −(2/21.8)

e) (2/21.8) e ^ (−120)

ii. How much of the sample remains (mg) after 14 years?

a) 76.88893.055

b) 109.222

c) 65.355

iii. After how many years will only 23 mg remain?

a) 48.32

b) 44.683

c) 70.142

d) 51.957

Given that a solution containing a 0.2 M concentration of a weak acid and 0.5 M of the negatively charged ion has a pH value of 4.4, find the pK value of the weak acid. Express the result to two decimal places.

For most species of fish, the mass M (in kg) is related to the body length L (in m) by the power-law relationshipcM=k×L3 where k is a constant. A young fish has a mass of 2.8 kg and a length of 70 cm.

(a) What is the mass in kg of an adult fish whose length is 130 cm? Give the answer to at least 3 significant figures.

(b) What is the length in m of a fish whose mass is 7 kg? Give the answer to at least 3 significant figures.

according to KMT, gases consists of subatomic particles called?

According to Kinetic Molecular Theory, gases consists of subatomic particles cal

led