Question 1

Which of the following best describes a double replacement reaction?

Accepted Answer

Two compounds exchange ions to form two new compounds.

Question 2

Given the reaction $$2H_2 + O_2$ \rightarrow 2H_2O$$, how many grams of water are produced when 8.0 g of hydrogen gas reacts completely with excess oxygen? (Molar mass of $$H_2 = 2.0$ g/mol, H_2O = 18.0$ g/mol)

Accepted Answer

$$72 g$$

Question 3

Which of the following reactions is an example of a decomposition reaction?

Accepted Answer

$$2H_2O_2 \xrightarrow{light} 2H_2O + O_2$

Question 4

A student mixes solutions of potassium iodide and lead(II) nitrate. A yellow solid forms. What type of reaction has occurred?

Accepted Answer

Double replacement (precipitation)

Question 5

Which of the following statements about exothermic reactions is correct?

Accepted Answer

The enthalpy change $$\Delta H is $$negative.

Question 6

How many molecules are present in $$0.256$$ mol of copper atoms? (Avogadro's number $$= 6.02 	imes 10$$^{23}$$)

Accepted Answer

$$1.54 	imes 10$$^{23}$$

Question 7

Which of the following is the correct balanced equation for the combustion of propane ($$C_3H_8$$)?

Accepted Answer

$$C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O$$

Question 8

A reaction has $$\Delta H = +678 kJ. $$Which of the following is true?

Accepted Answer

The reaction is endothermic and absorbs energy.

Question 9

What is the molar mass of $$Ca(OH)_2$$? (Atomic masses: $$Ca = 40.08$$, $$O = 16.00$$, $$H = 1.008)$$

Accepted Answer

$$74.10 g/$$mol

Question 10

Which of the following best explains why the atomic mass of chlorine is not a whole number?

Accepted Answer

It is the weighted average of the masses of all naturally occurring isotopes.

Question 11

If $$3.0$$ mol of $$NH_3$$ are present, how many grams of $$NH_3 is $$this? (Molar mass of $$NH_3 = 17.03$ g/mol)

Accepted Answer

$$51.09 g$$

Question 12

Which of the following is a single replacement reaction?

Accepted Answer

$$Zn + $$CuSO_4$$ \rightarrow Cu + $$ZnSO_4$$

Question 13

How many moles of $$CaCO_3$$ are present in $$150 g of$$ $$CaCO_3$$? (Molar mass $$= 100.09 g/$$mol)

Accepted Answer

$$0.667$$ mol

Question 14

Which of the following best describes a combination reaction?

Accepted Answer

Two or more reactants combine to form one product.

Question 15

In the reaction $$2Na + Cl_2$ \rightarrow 2NaCl$$, what mass of $$Na (in $$grams) is required to react with $$71.0 g of$$ $$Cl_2$$? (Molar mass: $$Na = 23.0 g/$$mol, $$Cl_2 = 71.0$ g/mol)

Accepted Answer

$$46.0 g$$

Question 16

Which of the following is the correct net ionic equation for the precipitation of silver chloride from solutions of silver nitrate and sodium chloride?

Accepted Answer

$$Ag^+ (aq) + Cl^- (aq) \rightarrow AgCl(s)$$

Question 17

A chemical reaction absorbs energy from its surroundings. Which of the following statements is true?

Accepted Answer

The reaction is endothermic and $$\Delta H is $$positive.

Question 18

Which of the following best represents Avogadro's number?

Accepted Answer

$$6.02 	imes 10$$^{23}$$

Question 19

If $$2.51$$ mol of $$CH_4$$ are present, how many molecules of $$CH_4 is $$this? (Avogadro's number $$= 6.02 	imes 10$$^{23}$$)

Accepted Answer

$$1.51 	imes 10$$^{24}$$

Chapter 5: Chemical Reactions – Study Notes

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