$$+1.60 \times 10$$^{-19}$$\ \mathrm{C}$$

$$\text{Atomic mass} = \sum x_i m_i$$

Question 1

Which of the following best describes a chemical change?

Accepted Answer

Iron nails rusting when exposed to oxygen.

Question 2

Which statement about the Law of Conservation of Mass is correct?

Accepted Answer

Matter is neither created nor destroyed, but can be transformed from one form to another.

Question 3

A student measures the mass of a sample three times and gets values very close to each other, but far from the actual mass. This demonstrates:

Accepted Answer

Low accuracy and high precision.

Question 4

Which of the following is a derived SI unit?

Accepted Answer

Meter per second squared ($$\mathrm{m/s^2$})$$

Question 5

Which of the following numbers has four significant figures?

Accepted Answer

0.0540

Question 6

A sample of water contains 16.0 g of oxygen and 2.0 g of hydrogen. What is the mass ratio of oxygen to hydrogen in water?

Accepted Answer

$$8:1$$

Question 7

Which scientist is credited with discovering the electron using the cathode ray tube experiment?

Accepted Answer

J.J. Thomson

Question 8

What is the charge of a proton?

Accepted Answer

$$+1.60 	imes 10$$^{-19}$$\ \mathrm{C}$$

Question 9

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same atomic number but different mass numbers.

Question 10

Which element is most likely to react explosively with water?

Accepted Answer

Sodium

Question 11

A neutral atom of sodium ($$\mathrm{Na}) $$has 11 protons. How many electrons does it have?

Accepted Answer

11

Question 12

Which of the following best describes the process of dimensional analysis?

Accepted Answer

Using conversion factors to cancel units and solve problems.

Question 13

What is Avogadro's number?

Accepted Answer

$$6.022 	imes 10$$^{23}$$

Question 14

Which of the following is a physical change?

Accepted Answer

Boiling water to produce steam.

Question 15

Which of the following elements is a noble gas?

Accepted Answer

Neon

Question 16

If you have $$2.45$$ mol of copper atoms, how many atoms do you have?

Accepted Answer

$$1.48 	imes 10$$^{24}$$

Question 17

Which scientist developed the periodic table with gaps for undiscovered elements?

Accepted Answer

Dmitri Mendeleev

Question 18

Which of the following is the correct formula for calculating atomic mass from isotopic abundances?

Accepted Answer

$$	ext{Atomic mass} = \sum x_i m_i$$

Question 19

Which of the following statements about ions is correct?

Accepted Answer

Cations are positively charged ions formed when an atom loses electrons.

Question 20

Which of the following best explains why elements heavier than iron are formed in supernovas?

Accepted Answer

Fusion in stars can only produce elements up to iron; heavier elements require the energy of a supernova.

Measurement, Physical and Chemical Change: Foundations of General Chemistry

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