Q: Which of the following is the correct percent yield if 1.03 g of water is collected from a reaction that theoretically produces 4.86 g?

$$\frac{1.03}{4.86} \times 100 = 21.2\%$$

Question 1

Which of the following best describes the difference between an element, a compound, and an ion?

Accepted Answer

An element is a pure substance made of only one kind of atom, a compound is a substance made of two or more elements chemically bonded, and an ion is an atom or molecule with a net electric charge.

Question 2

Which of the following is the correct balanced equation for the combustion of methane ($$CH_4) in $$oxygen?

Accepted Answer

$$CH_4 + 2O_2$$ \rightarrow $$CO_2 + 2H_2O$

Question 3

Given the reaction $$2Al(s) + 3H_2SO_4(aq) \rightarrow Al_2$(SO_4$)_3(aq) + 3H_2(g)$$, how many moles of $$H_2SO_4$$ are required to completely react with 4 moles of $$Al$$?

Accepted Answer

6 moles

Question 4

Which of the following statements about balancing chemical equations is correct?

Accepted Answer

Only the coefficients in front of compounds or elements can be changed to balance an equation.

Question 5

What is the mass of $$CO_2$$ produced when $$5.0 	imes 10^2$ g of octane (C_8H$$_{18}$$, molar mass = 114.3 g/mol) is completely combusted? (Use the equation: 2C_8H$$_{18} + 25O_2 ightarrow 16CO_2 + 18H_2O$$, CO_2$ molar mass = 44.01 g/mol)

Accepted Answer

$$1.5 	imes 10^3$ g

Question 6

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

Accepted Answer

BrCl

Question 7

What is the limiting reactant when 0.552 mol of $$Al$$ reacts with 0.887 mol of $$Cl_2 to $$form $$AlCl_3$$? (Equation: $$2Al + 3Cl_2 \rightarrow 2AlCl_3)$$

Accepted Answer

$$Cl_2$$

Question 8

Which of the following best describes the role of coefficients in a chemical equation?

Accepted Answer

They indicate the relative number of molecules or moles of each substance involved in the reaction.

Question 9

If 53.2 g of $$Na ($$molar mass = 22.99 g/mol) and 65.8 g of $$Cl_2 ($$molar mass = 70.90 g/mol) are reacted to form $$NaCl ($$molar mass = 58.44 g/mol), what is the theoretical yield of $$NaCl in $$grams? (Equation: $$2Na + Cl_2$ \rightarrow 2NaCl)$$

Accepted Answer

108 g

Question 10

Which of the following is the correct formula for chromium(VI) chloride?

Accepted Answer

$$CrCl_6$$

Question 11

A solution is labeled as 1.00 M KCl and you need to prepare 200 mL. What mass of KCl (molar mass = 74.55 g/mol) is required?

Accepted Answer

14.91 g

Question 12

Which of the following is the correct percent yield if 1.03 g of water is collected from a reaction that theoretically produces 4.86 g?

Accepted Answer

$$\frac{1.03}{4.86} 	imes 100 = 21.2\%$$

Question 13

Which of the following is a correct statement about the law of conservation of mass as applied to chemical reactions?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 14

Which of the following is the correct name for $$HNO_3$$?

Accepted Answer

Nitric acid

Question 15

If you have 15.0 g of $$Na_2CO_3 ($$molar mass = 105.99 g/mol) and 8.00 g of $$HCl ($$molar mass = 36.46 g/mol), how many grams of $$CO_2 ($$molar mass = 44.01 g/mol) can be produced? (Equation: $$Na_2CO_3 + 2HCl \rightarrow 2NaCl + H_2O + CO_2$)

Accepted Answer

2.42 g

Question 16

Which of the following is the correct state symbol for a substance dissolved in water?

Accepted Answer

$$(aq)$$

Question 17

Which of the following is a metal?

Accepted Answer

Pb

Question 18

What is the correct formula for nitrogen dioxide?

Accepted Answer

$$NO_2$$

Question 19

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

Accepted Answer

The reactant that is completely consumed and limits the amount of product formed.

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