Q: A sample of 508.4 grams of copper completely reacted with oxygen to form 572.4 grams of a copper oxide product. How many grams of oxygen must have reacted?

$$572.4\ \text{g} - 508.4\ \text{g} = 64.0\ \text{g}$$

Q: If $$100.0\ \text{J} of $$energy is absorbed by a $$26.2\ \text{g}$$ sample of metal, causing its temperature to rise by $$8.5^{\circ}$$\text{C}$$, what is the specific heat (c$) of the metal? Use the formula: q = mc$$\Delta T$$

$$c = \dfrac{100.0}{26.2 \times 8.5} = 0.235\ \text{J/g}^{\circ}\text{C}$$

Q: A chemical reaction absorbs $$575.0$$ kilocalories of energy. How many joules is this? ($$1\ \text{Calorie} = 4.184\ \text{J}$$, $$1\ \text{kcal} = 1000\ \text{Cal})$$

$$575.0 \times 1000 \times 4.184 = 2,402,800\ \text{J}$$

Q: If $$100.0\ \text{J} of $$energy is absorbed by a $$26.2\ \text{g}$$ sample of copper ($$c = 0.385\ \text{J/g}^{\circ}\text{C}$$), what is the temperature change ($$\Delta T$$)? Use $$q = mc\Delta T.$$

$$\Delta T = \dfrac{100.0}{26.2 \times 0.385} = 9.98$$^{\circ}$$\text{C}$$

Question 1

A sample of 508.4 grams of copper completely reacted with oxygen to form 572.4 grams of a copper oxide product. How many grams of oxygen must have reacted?

Accepted Answer

$$572.4\ 	ext{g} - 508.4\ 	ext{g} = 64.0\ 	ext{g}$$

Question 2

How many Calories are in 575.0 kilocalories?

Accepted Answer

$$575,000\ 	ext{Calories}$$

Question 3

Given the table of specific heat values below, what is the identity of a 26.2 g metal sample that increases by $$8.5^{\circ}$$	ext{C}$$ when 100.0$$\ 	ext{J}$$ of energy is absorbed?

Element | Specific Heat (J/g.$$^{\circ}$$C)
Au | 0.128
Ag | 0.235
Cu | 0.385

Accepted Answer

Silver (Ag)

Question 4

Which of the following best describes the law of conservation of mass as demonstrated in the reaction of copper with oxygen to form copper oxide?

Accepted Answer

The total mass of reactants equals the total mass of products.

Question 5

If $$100.0\ 	ext{J} of $$energy is absorbed by a $$26.2\ 	ext{g}$$ sample of metal, causing its temperature to rise by $$8.5^{\circ}$$	ext{C}$$, what is the specific heat (c$) of the metal?

Use the formula: q = mc$$\Delta T$$

Accepted Answer

$$c = \dfrac{100.0}{26.2 	imes 8.5} = 0.235\ 	ext{J/g}^{\circ}	ext{C}$$

Question 6

Which of the following statements about specific heat is correct?

Accepted Answer

A substance with a high specific heat requires more energy to change its temperature.

Question 7

A chemical reaction absorbs $$575.0$$ kilocalories of energy. How many joules is this? ($$1\ 	ext{Calorie} = 4.184\ 	ext{J}$$, $$1\ 	ext{kcal} = 1000\ 	ext{Cal})$$

Accepted Answer

$$575.0 	imes 1000 	imes 4.184 = 2,402,800\ 	ext{J}$$

Question 8

Which of the following is a physical property that can be used to identify a metal sample?

Accepted Answer

Specific heat capacity

Question 9

If $$100.0\ 	ext{J} of $$energy is absorbed by a $$26.2\ 	ext{g}$$ sample of copper ($$c = 0.385\ 	ext{J/g}^{\circ}	ext{C}$$), what is the temperature change ($$\Delta T$$)?

Use $$q = mc\Delta T.$$

Accepted Answer

$$\Delta T = \dfrac{100.0}{26.2 	imes 0.385} = 9.98$$^{\circ}$$	ext{C}$$

Question 10

Which of the following best explains why copper is used in electrical wiring?

Accepted Answer

Copper has a low specific heat and high electrical conductivity.

Question 11

A student claims that the mass of copper oxide formed should be less than the mass of copper used. Is this correct? Why or why not?

Accepted Answer

No, because oxygen from the air combines with copper, increasing the total mass.

Question 12

Which equation correctly relates energy, mass, specific heat, and temperature change?

Accepted Answer

$$q = mc\Delta T$$

Chemistry: Matter and Energy – Guided Practice

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