question 1
which element is found the fifth period and the first group of the periodic table?
question 2
how many atoms are in al₂(so₄)₃?
question 3
a 58 g sample of nacl contains 23 g of sodium. what is the percent composition of chlorine?
question 4
steel, an alloy of iron and other elements, can be classified as what type of mixture?
question 5
what phase change occurs when ice crystals (like snowflakes) form directly from water vapor in high-altitude clouds?
question 6
the statement “the solution turned blue when copper sulfate was added” is what type of observation?
question 7
how many significant figures are in the number 0.07040?
question 8
a sample of ethanol has a mass of 46 g and a density of 0.79 g/ml. what is its volume?

Question

Accepted Answer

### QUESTION 1
# Brief Explanations:
The periodic table's groups (vertical columns) and periods (horizontal rows) help identify elements. Group 1 (alkali metals) has elements with one valence electron. The fifth period means the element is in the 5th row. Rubidium (Rb) is in period 5, group 1.
# Answer:
Rubidium (Rb)

### QUESTION 2
# Explanation:
## Step1: Analyze each part
In $\ce{Al2(SO4)3}$, for Al: coefficient 2, so 2 atoms. For $\ce{SO4}$: inside the parenthesis, S is 1, O is 4, and the subscript 3 outside multiplies the $\ce{SO4}$ group. So S: $1	imes3 = 3$, O: $4	imes3 = 12$.
## Step2: Sum all atoms
Total atoms = Al + S + O = $2 + 3 + 12 = 17$.
# Answer:
17

### QUESTION 3
# Explanation:
## Step1: Find mass of Cl
Mass of NaCl is 58 g, mass of Na is 23 g. So mass of Cl = $58 - 23 = 35$ g.
## Step2: Calculate percent composition
Percent composition of Cl = $\frac{	ext{mass of Cl}}{	ext{mass of NaCl}} 	imes 100\% = \frac{35}{58} 	imes 100\% \approx 60.34\%$ (or using exact values, since NaCl has molar mass 58.44 g/mol, Na is 22.99 g/mol, Cl is 35.45 g/mol. Percent Cl = $\frac{35.45}{58.44} 	imes 100\% \approx 60.66\%$, but with the given 58g and 23g, it's $\frac{35}{58} 	imes 100 \approx 60.3\%$ or more accurately, since 58 - 23 = 35, $\frac{35}{58} 	imes 100 = \frac{3500}{58} \approx 60.34\%$).
# Answer:
Approximately 60.3% (or 60.6% if using molar masses, but with given data, 35/58*100 ≈ 60.3%)

### QUESTION 4
# Brief Explanations:
Steel is a homogeneous mixture (solution) because the components (iron, carbon, etc.) are uniformly distributed at the atomic/molecular level, and it has a uniform appearance and properties throughout. Alloys like steel are solid solutions, so they are homogeneous mixtures.
# Answer:
Homogeneous mixture (or solid solution)

### QUESTION 5
# Brief Explanations:
Deposition is the phase change where a gas changes directly to a solid without passing through the liquid phase. Water vapor (gas) forming ice crystals (solid) directly is deposition.
# Answer:
Deposition

### QUESTION 6
# Brief Explanations:
A qualitative observation describes a quality or characteristic (like color, shape, etc.) without using numbers. The statement describes the color change, so it's a qualitative observation.
# Answer:
Qualitative observation

### QUESTION 7
# Explanation:
## Step1: Recall significant figure rules
Leading zeros are not significant. Zeros between non - zero digits are significant. Trailing zeros after a decimal are significant.
## Step2: Analyze 0.07040
- Leading zeros: 0.0 are not significant.
- 7 is significant, 0 between 7 and 4 is significant, 4 is significant, trailing 0 after 4 is significant.
- So significant figures: 7, 0, 4, 0 → 4 significant figures? Wait, no: 0.07040. Let's count:
  - The first non - zero digit is 7. Then 0 (between 7 and 4) is significant, 4 is significant, and the trailing 0 (after 4, and after decimal) is significant. So digits: 7, 0, 4, 0. Wait, no: 0.07040. Let's write the number in scientific notation: $7.040	imes10^{-2}$. The digits in scientific notation are 7, 0, 4, 0. So that's 4 significant figures? Wait, no: 0.07040. Let's count:
    - Leading zeros: 2 (the two zeros before 7) → not significant.
    - 7: significant.
    - 0: between 7 and 4 → significant.
    - 4: significant.
    - 0: trailing zero after decimal → significant.
    So total significant figures: 4? Wait, no, 0.07040: the digits are 7, 0, 4, 0. Wait, 7 (1), 0 (2), 4 (3), 0 (4). So 4 significant figures? Wait, no, maybe I made a mistake. Wait, 0.07040: let's see, the number is 0.07040. The rules:
    - All non - zero digits are significant: 7, 4 → 2.
    - Zeros between non - zero digits: the 0 between 7 and 4 → 1 (total 3).
    - Trailing zeros in the decimal part: the last 0 → 1 (total 4).
    So yes, 4 significant figures? Wait, no, wait 0.07040: the first non - zero is 7. Then 0 (between 7 and 4) is significant, 4 is significant, and the trailing 0 (after 4, and after the decimal) is significant. So that's 4 significant figures. Wait, but let's check with an example: 0.07040. The zeros before 7 are leading, not significant. The 0 between 7 and 4 is significant (because it's between two non - zero digits). The 4 is significant. The trailing 0 (after 4, in the decimal) is significant. So total: 7, 0, 4, 0 → 4 significant figures.
# Answer:
4

### QUESTION 8
# Explanation:
## Step1: Recall density formula
Density ($
ho$) is given by $
ho=\frac{m}{V}$, where $m$ is mass and $V$ is volume. We need to find $V$, so rearrange the formula to $V = \frac{m}{
ho}$.
## Step2: Substitute values
Given $m = 46$ g and $
ho=0.79$ g/mL. So $V=\frac{46}{0.79}\approx58.23$ mL (or using exact calculation: $46\div0.79=\frac{4600}{79}\approx58.23$ mL).
# Answer:
Approximately 58 mL (or 58.2 mL)

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QUESTION IMAGE

Question

Explanation:

QUESTION 1

Step1: Analyze each part

Step2: Sum all atoms

Step1: Find mass of Cl

Step2: Calculate percent composition

Answer:

QUESTION 2