Q: A sample contains 2.45 mol of copper (Cu). If the molar mass of Cu is $$63.546 \ \mathrm{g/mol}$$, what is the mass of the sample?

$$2.45 \times 63.546 = 155.68 \ \mathrm{g}$$

Q: How many atoms are present in $$2.00$$ mol of $$\mathrm{H}_2\mathrm{O}$$?

$$2.00 \times 6.022 \times 10$$^{23}$$ \times 3 = 3.61 \times 10$$^{24}$$ atoms

Question 1

Which of the following statements best describes a chemical change?

Accepted Answer

It involves a change in the atomic arrangement, resulting in new substances.

Question 2

A sample contains 2.45 mol of copper (Cu). If the molar mass of Cu is $$63.546 \ \mathrm{g/mol}$$, what is the mass of the sample?

Accepted Answer

$$2.45 	imes 63.546 = 155.68 \ \mathrm{g}$$

Question 3

Which of the following is the correct empirical formula for a compound with 60.00% C, 4.48% H, and 35.52% O by mass?

Accepted Answer

$$\mathrm{C}_2\mathrm{H}_3\mathrm{O}$$

Question 4

Which of the following ions is a cation?

Accepted Answer

$$\mathrm{Na}^+$$

Question 5

Calculate the average atomic mass of neon given the following isotopic abundances: $$^{20}\mathrm{Ne} (90.48$$%), $$^{21}\mathrm{Ne} (0.27$$%), $$^{22}\mathrm{Ne} (9.25$$%).

Accepted Answer

$$20.19 \ \mathrm{g/mol}$$

Question 6

Which of the following compounds is an example of a molecular (covalent) compound?

Accepted Answer

$$\mathrm{CO}_2$$

Question 7

What is the correct name for $$\mathrm{N}_2\mathrm{O}_4$$?

Accepted Answer

Dinitrogen tetroxide

Question 8

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons

Question 9

What is the formula for the ionic compound formed between aluminum and oxygen?

Accepted Answer

$$\mathrm{Al}_2\mathrm{O}_3$$

Question 10

Which of the following is the correct molecular formula for a compound with an empirical formula of $$\mathrm{C}_2\mathrm{H}_3\mathrm{O}$$ and a molar mass of $$86.09 \ \mathrm{g/mol}$$?

Accepted Answer

$$\mathrm{C}_4\mathrm{H}_6\mathrm{O}_2$$

Question 11

Which of the following ions is polyatomic?

Accepted Answer

$$\mathrm{NO}_3^-$$

Question 12

How many atoms are present in $$2.00$$ mol of $$\mathrm{H}_2\mathrm{O}$$?

Accepted Answer

$$2.00 	imes 6.022 	imes 10$$^{23}$$ 	imes 3 = 3.61 	imes 10$$^{24}$$ atoms

Question 13

Which of the following is the correct name for $$\mathrm{FePO}_3$$?

Accepted Answer

Iron (III) phosphate

Question 14

Which of the following best describes the trend for ionic charge among Group 1 elements in the periodic table?

Accepted Answer

They form $$+1$$ ions.

Question 15

What is the correct formula for ammonium nitrate?

Accepted Answer

$$\mathrm{NH}_4\mathrm{NO}_3$$

Question 16

Which of the following is the correct name for $$\mathrm{Ca($$BrO_4$$)_2}$$?

Accepted Answer

Calcium perbromate

Question 17

A neutral atom of chlorine has an atomic number of 17 and a mass number of 35. How many neutrons does it have?

Accepted Answer

$$35 - 17 = 18$$ neutrons

Question 18

Which of the following is the correct formula for chromium (III) carbonate?

Accepted Answer

$$\mathrm{Cr}_2(\mathrm{CO}_3)_3$$

Question 19

Which of the following best describes the difference between a compound and a mixture?

Accepted Answer

A compound has a fixed composition and chemical bonds between elements, while a mixture does not.

Atoms, Elements, Compounds, and Chemical Bonds: Essential Concepts for General Chemistry

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