Question 1

Which of the following is a chemical property?

Accepted Answer

The tendency of iron to rust when exposed to air.

Question 2

A student slices an apple and observes that it turns brown after a few minutes. Which statement best explains the changes observed?

Accepted Answer

Slicing is a physical change, but browning is a chemical change due to a reaction with oxygen.

Question 3

At what Celsius temperature will the numerical reading on a Fahrenheit thermometer be one-eighth that on a Celsius thermometer? (Use $$F = \frac{9}{5}C + 32)$$

Accepted Answer

$$C = -4.57^\circ$$

Question 4

Convert the temperature $$-4.57^\circC to $$Kelvin.

Accepted Answer

$$K = 268.58$$

Question 5

Student A measures a 100.0-g standard mass five times and gets: 104.2 g, 104.1 g, 104.3 g, 104.2 g, 104.2 g. Student B gets: 97.1 g, 98.4 g, 99.0 g, 102.5 g, 106.0 g. Which statement best describes the errors in their measurements?

Accepted Answer

Student A shows a dominant systematic error (high precision, low accuracy); Student B shows a dominant random error (low precision, variable accuracy).

Question 6

A swimming pool contains 18,000 gallons of water. To achieve a chlorine level of 1 ppm using a 7.0% chlorine solution (density $$1.10\ \mathrm{g/mL}$$), how many liters of the solution are needed? ($$1\ \mathrm{gallon} = 3.785\ \mathrm{L}$$, pool water density $$1.00\ \mathrm{g/mL})$$

Accepted Answer

$$0.98\ \mathrm{L}$$

Question 7

Iodine-123 and Iodine-131 are used in medicine. How many neutrons, protons, and electrons are in a single $$^{123}\mathrm{I}^-$$ ion?

Accepted Answer

70 neutrons, 53 protons, 54 electrons

Question 8

A 2.500 g sample of a hydrocarbon contains 1.000 g C and 0.167 g H. What is the mass of oxygen in the sample?

Accepted Answer

$$1.333\ \mathrm{g}$$

Question 9

Given the same sample (2.500 g, 1.000 g C, 0.167 g H, 1.333 g O), what is the mass percent of hydrogen?

Accepted Answer

$$6.68\%$$

Question 10

Convert the mass of each element in the sample to moles. Which is the correct number of moles of carbon?

Accepted Answer

$$0.0833\ \mathrm{mol}$$

Question 11

Given the mole ratios from the previous question (C: $$0.0833$$, H: $$0.1658$$, O: $$0.0833$$), what is the empirical formula of the compound?

Accepted Answer

$$\mathrm{C_1H_2O_1}$$

Question 12

If the empirical formula is $$\mathrm{CH_2O}$$ and the molar mass is approximately $$180\ \mathrm{g/mol}$$, what is the molecular formula?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$}$$

Question 13

Why are the empirical formula and molecular formula of a compound not always identical?

Accepted Answer

The empirical formula shows the simplest whole-number ratio of atoms, while the molecular formula shows the actual number of atoms in a molecule.

Question 14

Which of the following best describes a physical property?

Accepted Answer

A sapphire is blue.

Question 15

A slab of marble feels cool to the touch. This is an example of:

Accepted Answer

A physical property, because it relates to heat transfer and not a change in composition.

Question 16

Which of the following is an example of a dominant systematic error in a laboratory setting?

Accepted Answer

A scale that is improperly zeroed, causing all measurements to be off by the same amount.

Question 17

Which of the following best describes the relationship between accuracy and precision?

Accepted Answer

Accuracy refers to how close measurements are to the true value, while precision refers to how close measurements are to each other.

Question 18

Which of the following best explains why significant figures are important in scientific measurements?

Accepted Answer

They reflect the precision of the measurement and prevent overstatement of certainty.

General Chemistry Problem Set 1: Step-by-Step Study Guidance

Guida di studio - Domande di pratica

Study guide - Flashcard