Q: A sample of magnesium contains 24.305 g. How many atoms of magnesium are present? ($$\mathrm{M_{Mg}} = 24.305\ \mathrm{g/mol})$$

$$6.022 \times 10$$^{23}$$ atoms

Question 1

A sample of an unknown metal has a mass of 45.6 g and displaces 16.2 mL of water when submerged. What is the density of the metal in $$\mathrm{g/cm^3$}$$? (Assume $$1\ \mathrm{mL} = 1\ \mathrm{cm^3$}.)$$

Accepted Answer

$$2.82\ \mathrm{g/cm^3$}$$

Question 2

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 3

A compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is the empirical formula of the compound?

Accepted Answer

$$\mathrm{CH_2O}$$

Question 4

Which of the following is a derived SI unit?

Accepted Answer

$$\mathrm{m^3$} ($$cubic meter)

Question 5

A student measures the mass of a sample as 12.30 g and its volume as 4.0 mL. How many significant figures should the calculated density have?

Accepted Answer

2

Question 6

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

Accepted Answer

J.J. Thomson

Question 7

What is the molar mass of $$\mathrm{Ca(NO_3$)_2}$$?

Accepted Answer

$$164.10\ \mathrm{g/mol}$$

Question 8

Which of the following best describes a heterogeneous mixture?

Accepted Answer

A mixture in which the composition is not uniform throughout

Question 9

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of $$\mathrm{$$CO_2$$}$$. How many moles of $$\mathrm{$$CO_2$$}$$ are present?

Accepted Answer

$$0.500\ \mathrm{mol}$$

Question 10

Which of the following ions is isoelectronic with neon ($$\mathrm{Ne}$$)?

Accepted Answer

$$\mathrm{F^-}$$

Question 11

A student needs to prepare 250.0 mL of a 0.200 M NaCl solution. How many grams of NaCl are required? ($$\mathrm{M_{NaCl}} = 58.44\ \mathrm{g/mol})$$

Accepted Answer

$$2.92\ \mathrm{g}$$

Question 12

Which of the following is the correct name for $$\mathrm{Fe_2O_3}$$?

Accepted Answer

Iron(III) oxide

Question 13

Which of the following statements about exact and measured numbers is correct?

Accepted Answer

Exact numbers have no uncertainty and do not limit the number of significant figures in a calculation.

Question 14

A sample of magnesium contains 24.305 g. How many atoms of magnesium are present? ($$\mathrm{M_{Mg}} = 24.305\ \mathrm{g/mol})$$

Accepted Answer

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

Question 15

Which of the following best describes the law of definite proportions?

Accepted Answer

A given compound always contains the same proportion of elements by mass.

Question 16

A 5.00 g sample of a compound contains 2.00 g of hydrogen and 3.00 g of oxygen. What is the percent by mass of hydrogen in the compound?

Accepted Answer

$$40.0\%$$

Question 17

Which of the following is the correct formula for aluminum sulfate?

Accepted Answer

$$\mathrm{Al_2$(SO_4$)_3}$$

Question 18

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

Accepted Answer

A molecule consists of two or more atoms bonded together, while a compound contains atoms of different elements.

Question 19

A patient receives an intravenous solution containing 0.90% NaCl by mass. If the patient receives 500.0 mL of this solution (density = $$1.00\ \mathrm{g/mL}$$), how many grams of NaCl does the patient receive?

Accepted Answer

$$4.5\ \mathrm{g}$$

Question 20

Which of the following elements is a halogen?

Accepted Answer

Chlorine

CHEM 141 Exam 1 Study Guide: Matter, Atoms, and Molecules

Guida di studio - Domande di pratica

Study guide - Flashcard