Q: How many molecules are present in $$4$$ moles of $$\mathrm{AlCl}_3$$?

$$2.4 \times 10$$^{24}$$ molecules

Question 1

A student measures the mass of a sample four times and obtains the following values: 2.924 g, 2.923 g, 2.925 g, and 2.926 g. The true mass is 2.700 g. Which statement best describes the student's measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 2

Which of the following numbers contains exactly three significant figures?

Accepted Answer

$$1.42 	imes 10^5$

Question 3

A student records the temperature of a solution as $$79^\circ C$$, but the true value is $$85^\circ C. $$What is the percent error in the student's measurement?

Accepted Answer

$$7.1\%$$

Question 4

How many milligrams are there in $$0.53 kg$$?

Accepted Answer

$$5.3 	imes 10^5$ mg

Question 5

Which of the following best describes an isotope?

Accepted Answer

Atoms of the same element with different numbers of neutrons.

Question 6

A neutral atom of copper-65 ($$^{65}Cu) $$has how many protons, neutrons, and electrons?

Accepted Answer

29 protons, 36 neutrons, 29 electrons

Question 7

Chlorine has two main isotopes: $$^{35}Cl ($$mass = $$34.97 u$$, abundance = $$75.8\%) $$and $$^{37}Cl ($$mass = $$36.97 u$$, abundance = $$24.2\%). $$What is the average atomic mass of chlorine?

Accepted Answer

$$35.47 u$$

Question 8

How many molecules are present in $$4$$ moles of $$\mathrm{AlCl}_3$$?

Accepted Answer

$$2.4 	imes 10$$^{24}$$ molecules

Question 9

What is the molar mass of $$\mathrm{H}_2\mathrm{CO}_3 ($$carbonic acid)? (Atomic masses: H = $$1.01 g/$$mol, C = $$12.01 g/$$mol, O = $$16.00 g/$$mol)

Accepted Answer

$$36.03 g/$$mol

Question 10

Which of the following is a homogeneous mixture?

Accepted Answer

Saltwater

Question 11

A $$30 g $$rock has a volume of $$6.7 mL. $$What is its density?

Accepted Answer

$$4.48 g/mL$$

Question 12

Which of the following best describes a cation?

Accepted Answer

An atom that has lost electrons

Question 13

Which of the following is the correct name for $$\mathrm{FeCl}_3$$?

Accepted Answer

Iron(III) chloride

Question 14

Which of the following is the correct formula for dinitrogen pentoxide?

Accepted Answer

$$\mathrm{N}_2\mathrm{O}_5$$

Question 15

A $$12 kg $$object has a weight force of $$588 N on $$planet X. What is the gravitational acceleration on planet X?

Accepted Answer

$$9.8 m/s$^2$$

Question 16

Which of the following is a property of a compound but NOT a mixture?

Accepted Answer

Has a fixed composition

Question 17

What is the correct name for $$\mathrm{HNO}_3$$?

Accepted Answer

Nitric acid

Question 18

How many moles of hydrogen atoms are present in $$3 	imes 10$$^{24}$$ atoms of hydrogen?

Accepted Answer

$$5$$ mol

Question 19

Which of the following best describes the difference between an atom and a molecule?

Accepted Answer

An atom is the smallest part of an element, while a molecule is the smallest unit of a compound that retains its properties.

Question 20

Which group in the periodic table contains the noble gases?

Accepted Answer

Group 18

CHEM-1003: Measurement, Accuracy, Precision, and Significant Figures

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