Q: Which formula represents the calculation for percent yield in a chemical reaction?

$\text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%$

Q: Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

$\text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}}$

Question 1

Which of the following best defines chemistry?

Accepted Answer

The study of the composition, structure, properties, and changes of matter.

Question 2

Which statement correctly describes the Law of Conservation of Mass?

Accepted Answer

Mass is neither created nor destroyed in a chemical reaction.

Question 3

A student measures the mass of a sample as 12.345 g. How many significant figures are in this measurement?

Accepted Answer

5

Question 4

Which of the following is a physical change?

Accepted Answer

Melting ice into water

Question 5

Which formula represents the calculation for percent yield in a chemical reaction?

Accepted Answer

$	ext{Percent Yield} = \frac{	ext{Actual Yield}}{	ext{Theoretical Yield}} 	imes 100\%$

Question 6

Which of the following best describes an ionic compound?

Accepted Answer

A compound formed by the transfer of electrons from a metal to a nonmetal.

Question 7

Which of the following is the correct electron configuration for a neutral nitrogen atom?

Accepted Answer

$1s^2\ 2s^2\ 2p^3$

Question 8

A compound contains 40.0 g of carbon, 6.7 g of hydrogen, and 53.3 g of oxygen. What is the empirical formula of the compound?

Accepted Answer

$\mathrm{CH_2O}$

Question 9

Which of the following best explains why water is a polar molecule?

Accepted Answer

Water has a bent molecular shape and an uneven distribution of electron density.

Question 10

Which of the following is the correct balanced equation for the combustion of methane ($\mathrm{CH_4}$)?

Accepted Answer

$\mathrm{CH_4} + 2\mathrm{O_2} \rightarrow \mathrm{CO_2} + 2\mathrm{H_2O}$

Question 11

Which of the following elements has the highest electronegativity?

Accepted Answer

Fluorine

Question 12

A solution is prepared by dissolving 5.0 g of NaCl in enough water to make 250 mL of solution. What is the molarity of the solution? ($\mathrm{NaCl}$ molar mass = 58.44 g/mol)

Accepted Answer

$0.34\ \mathrm{M}$

Question 13

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between two nonmetal atoms.

Question 14

Which of the following is the correct formula for calculating the number of moles from mass and molar mass?

Accepted Answer

$	ext{Moles} = \frac{	ext{Mass}}{	ext{Molar Mass}}$

Question 15

Which of the following is a correct statement about atomic number?

Accepted Answer

It is equal to the number of protons in the nucleus of an atom.

Question 16

Which of the following is a correct statement about isotopes?

Accepted Answer

Isotopes are atoms of the same element with different numbers of neutrons.

Question 17

Which of the following best describes a limiting reactant in a chemical reaction?

Accepted Answer

The reactant that is completely consumed first, limiting the amount of product formed.

Question 18

Which of the following is the correct formula for calculating the energy of a photon?

Accepted Answer

$E = h 
u$

Question 19

Which of the following best describes the octet rule?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve eight electrons in their valence shell.

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