Q: How many calcium atoms are present in a $$0.6000-$$mol sample of Ca?

$$3.61 \times 10$$^{23}$$ atoms

Q: Which equation correctly relates mass, molar mass, and number of moles?

$$\text{mass} = \text{moles} \times \text{molar mass}$$

Q: Which of the following is the correct definition of molarity?

$$\text{Molarity} = \dfrac{\text{moles of solute}}{\text{liters of solution}}$$

Question 1

Which of the following best describes Avogadro's number?

Accepted Answer

The number of items (atoms, molecules, particles, etc.) in one mole, specifically $$6.022 	imes 10$$^{23}$$

Question 2

How many calcium atoms are present in a $$0.6000-$$mol sample of Ca?

Accepted Answer

$$3.61 	imes 10$$^{23}$$ atoms

Question 3

Which equation correctly relates mass, molar mass, and number of moles?

Accepted Answer

$$	ext{mass} = 	ext{moles} 	imes 	ext{molar mass}$$

Question 4

Calculate the molar mass of methane, CH$$_4.$$

Accepted Answer

$$16.04\ 	ext{g/mol}$$

Question 5

A sample contains $$4.05$$ mol of N$$_2O. $$What is its mass?

Accepted Answer

$$178\ 	ext{g}$$

Question 6

How many moles are in $$2.37 g of C$_7H$_8O$_2$$? (Molar mass = $$124.14\ 	ext{g/mol})$$

Accepted Answer

$$0.0191$$ mol

Question 7

Which of the following is the correct definition of molarity?

Accepted Answer

$$	ext{Molarity} = \dfrac{	ext{moles of solute}}{	ext{liters of solution}}$$

Question 8

What is the molarity of a solution prepared by dissolving $$7.85 g of $$methanol (CH$$_3OH$$, molar mass $$32.04\ 	ext{g/mol}) in$$ $$153 mL of $$solution?

Accepted Answer

$$0.161\ 	ext{M}$$

Question 9

What volume of $$12\ 	ext{M}$$ HCl must be taken to obtain $$0.10$$ mol of HCl?

Accepted Answer

$$8.3\ 	ext{mL}$$

Question 10

Which statement about balancing chemical equations is correct?

Accepted Answer

Only the coefficients can be changed; subscripts are fixed by the chemical nature of the reactants and products.

Question 11

Balance the following equation: $$P_2O_5 + H_2O \rightarrow H_3PO_4$$

Accepted Answer

$$P_2O_5 + 3H_2O \rightarrow 2H_3PO_4$$

Question 12

Which of the following is NOT a common type of reaction in aqueous solution?

Accepted Answer

Combustion reaction

Question 13

A solution is prepared by dissolving $$1.20$$ mol of NaCl in enough water to make $$2.50 L of $$solution. What is the concentration of NaCl?

Accepted Answer

$$0.480\ 	ext{M}$$

Question 14

Which step is NOT part of the process for writing a chemical equation?

Accepted Answer

Change the subscripts of compounds to balance the equation

Question 15

Which conversion factor would you use to convert from number of particles to moles?

Accepted Answer

Divide by Avogadro's number, $$N_A$$

Question 16

If you have $$2.00$$ mol of H$$_2$$ and $$3.00$$ mol of O$$_2$$, what is the limiting reactant in the reaction $$2H_2 + O_2$ \rightarrow 2H_2O$$?

Accepted Answer

H$$_2$$

Question 17

Which of the following is the correct molar mass for NaCl?

Accepted Answer

$$58.44\ 	ext{g/mol}$$

Question 18

A student dissolves $$0.10$$ mol of HCl in water to make $$250 mL of $$solution. What is the molarity?

Accepted Answer

$$0.40\ 	ext{M}$$

Mass Relations in Chemistry: Stoichiometry – Study Notes

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