Q: A student needs to convert $$250\ \mathrm{mg} to $$grams using unit cancellation. Which of the following is the correct calculation?

$$250\ \mathrm{mg} \times \frac{1\ \mathrm{g}}{1000\ \mathrm{mg}} = 0.250\ \mathrm{g}$$

Question 1

Which of the following best describes the difference between an exact number and a measured number?

Accepted Answer

An exact number is obtained by counting or by definition, while a measured number is obtained using a measuring device and has uncertainty.

Question 2

A patient’s body temperature is measured as $$39.2\ ^\circ\mathrm{C}. $$What is this temperature in Kelvin?

Accepted Answer

$$312.4\ \mathrm{K}$$

Question 3

Which of the following is a chemical change?

Accepted Answer

Iron rusting in moist air

Question 4

A nutrition label states that a snack contains 10 g of carbohydrates, 5 g of fat, and 3 g of protein. Calculate the total energy content in kilocalories ($$\mathrm{kcal}) $$using the following values: $$4\ \mathrm{kcal/g}$$ for carbohydrates, $$9\ \mathrm{kcal/g}$$ for fat, and $$4\ \mathrm{kcal/g}$$ for protein.

Accepted Answer

$$81\ \mathrm{kcal}$$

Question 5

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have similar chemical properties because they have the same number of valence electrons.

Question 6

How many protons, neutrons, and electrons are present in the isotope $$^{37}_{17}\mathrm{Cl}$$?

Accepted Answer

17 protons, 20 neutrons, 17 electrons

Question 7

Which of the following electron configurations represents a neutral atom of magnesium ($$\mathrm{Mg}$$, atomic number 12)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$

Question 8

A sample of metal has a mass of $$45.0\ \mathrm{g}$$ and a volume of $$15.0\ \mathrm{mL}. $$What is its density?

Accepted Answer

$$3.00\ \mathrm{g/mL}$$

Question 9

Which of the following best describes the trend in atomic size across a period from left to right?

Accepted Answer

Atomic size decreases due to increasing nuclear charge pulling electrons closer.

Question 10

Which of the following is the correct abbreviated electron configuration for bromine ($$\mathrm{Br}$$, atomic number 35)?

Accepted Answer

$$[\mathrm{Ar}]\ 4s^2$\ 3d$$^{10}$$\ 4p^5$

Question 11

A 50.0 g sample of water is heated from $$20.0\ ^\circ\mathrm{C} to$$ $$80.0\ ^\circ\mathrm{C}. If $$the specific heat of water is $$4.18\ \mathrm{J/g\ ^\circ C}$$, how much heat is absorbed?

Accepted Answer

$$12,540\ \mathrm{J}$$

Question 12

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 13

Which of the following best describes the electron arrangement in the $$p$$ orbitals?

Accepted Answer

There are three $$p$$ orbitals per energy level, each oriented along a different axis ($$x$$, $$y$$, $$z).$$

Question 14

Which of the following is a homogeneous mixture?

Accepted Answer

Saltwater

Question 15

How many valence electrons does an atom of sulfur ($$\mathrm{S}$$, atomic number 16) have?

Accepted Answer

6

Question 16

Which of the following best explains why ionization energy increases across a period?

Accepted Answer

The increasing nuclear charge holds electrons more tightly, requiring more energy to remove an electron.

Question 17

A student needs to convert $$250\ \mathrm{mg} to $$grams using unit cancellation. Which of the following is the correct calculation?

Accepted Answer

$$250\ \mathrm{mg} 	imes \frac{1\ \mathrm{g}}{1000\ \mathrm{mg}} = 0.250\ \mathrm{g}$$

Question 18

Which of the following is the correct electron-dot symbol for nitrogen ($$\mathrm{N}$$)?

Accepted Answer

A symbol with five dots: one pair and three single dots around the 'N'

Question 19

A sample contains $$75\%$$ $$^{35}\mathrm{Cl} ($$atomic mass $$34.97 u) $$and $$25\%$$ $$^{37}\mathrm{Cl} ($$atomic mass $$36.97 u). $$What is the average atomic mass of chlorine?

Accepted Answer

$$35.48\ \mathrm{u}$$

Chem 410 Exam 1 Study Guide: Chapters 1–4 (Chemistry in Our Lives, Measurements, Matter & Energy, Atoms & Elements)

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