Question

chapter 7 review
concept practice

1. list three common ways that matter is measured. give examples of each. 7.1
2. how many hydrogen atoms are in a representative particle of each substance? 7.1

a. $\text{al(oh)}_3$ c. $(\text{nh}_4)_2\text{hpo}_4$
b. $\text{h}_2\text{c}_2\text{o}_4$ d. $\text{c}_4\text{h}_{10}\text{o}$

1. which contains more molecules: 1.00 mol $\text{h}_2\text{o}_2$, 1.00 mol $\text{c}_2\text{h}_6$, or 1.00 mol $\text{co}$? 7.1
2. calculate the molar mass of each substance. 7.1

a. $\text{h}_3\text{po}_4$
b. $\text{n}_2\text{o}_3$

1. calculate the volume of each of the following gases at stp. 7.2

a. 7.6 mol $\text{ar}$
b. 0.44 mol $\text{c}_2\text{h}_6$
c. 1.20 mol $\text{o}_2$

Explanation:

Question 44

1. Mass: Measures the amount of matter; example: A 500g block of iron, measured with a balance.
2. Volume: Measures space occupied; example: 2 liters of water, measured with a graduated cylinder.
3. Amount (moles): Counts particles; example: 1 mole of carbon atoms (6.02×10²³ atoms).

Step1: Count H atoms in $Al(OH)_3$

Each $OH^-$ has 1 H; 3 $OH^-$: $3 \times 1 = 3$

Step2: Count H atoms in $H_2C_2O_4$

Subscript directly gives H count: $2$

Step3: Count H atoms in $(NH_4)_2HPO_4$

2 $NH_4^+$ have $2 \times 4 = 8$, plus 1 H: $8 + 1 = 9$

Step4: Count H atoms in $C_4H_{10}O$

Subscript gives H count: $10$

1 mole of any substance contains the same number of particles (Avogadro's number: $6.02 \times 10^{23}$ molecules). All samples are 1.00 mol, so they have equal numbers of molecules.

Answer:

1. Mass (example: 500g iron block)
2. Volume (example: 2L water)
3. Amount in moles (example: 1 mol C atoms)

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Question 46