Q: Calculate the percent composition by mass of oxygen in $$H_2O.$$

$$\frac{16.00}{18.02} \times 100\% = 88.8\%$$

Q: How many atoms are present in $$2.00\ mol of $$carbon?

$$2.00 \times 6.02 \times 10$$^{23}$$ = 1.20 \times 10$$^{24}$$ atoms

Q: What is the molar mass of $$Ca(NO_3$)_2$$?

$$40.08 + 2 \times (14.01 + 3 \times 16.00) = 164.10\ g/mol$$

Q: A student needs to convert $$250\ mg to $$grams using the factor-label method. Which of the following is correct?

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

Question 1

Which of the following is an example of a chemical change?

Accepted Answer

Iron rusting in moist air

Question 2

Which of the following statements about mixtures is correct?

Accepted Answer

A solution of salt in water is a homogeneous mixture.

Question 3

Which of the following is an extensive property?

Accepted Answer

Mass

Question 4

Convert a temperature of $$25\ ^\circ C to $$Kelvin.

Accepted Answer

$$25 + 273.15 = 298.15\ K$$

Question 5

A sample of gold has a mass of $$96.5\ g$$ and a volume of $$5.00\ cm^3$. What is its density?

Accepted Answer

$$19.3\ g/cm^3$

Question 6

Which of the following is the correct scientific notation for the number $$0.000456$$?

Accepted Answer

$$4.56 	imes 10$$^{-4}$$

Question 7

Which of the following elements is a noble gas?

Accepted Answer

Argon

Question 8

Which of the following compounds is named correctly?

Accepted Answer

NaCl: Sodium chloride

Question 9

What is the formula for the compound formed between aluminum and sulfate ion?

Accepted Answer

$$Al_2$$($$SO_4)_3$

Question 10

Calculate the percent composition by mass of oxygen in $$H_2O.$$

Accepted Answer

$$\frac{16.00}{18.02} 	imes 100\% = 88.8\%$$

Question 11

A hydrate of magnesium sulfate has a mass of $$13.52\ g$$ before heating and $$6.60\ g$$ after heating. What is the mass of water lost?

Accepted Answer

$$13.52\ g - 6.60\ g = 6.92\ g$$

Question 12

How many atoms are present in $$2.00\ mol of $$carbon?

Accepted Answer

$$2.00 	imes 6.02 	imes 10$$^{23}$$ = 1.20 	imes 10$$^{24}$$ atoms

Question 13

What is the molar mass of $$Ca(NO_3$)_2$$?

Accepted Answer

$$40.08 + 2 	imes (14.01 + 3 	imes 16.00) = 164.10\ g/mol$$

Question 14

How many moles are in $$44.8\ L of$$ $$CO_2$$ gas at STP?

Accepted Answer

$$\frac{44.8\ L}{22.4\ L/mol} = 2.00\ mol$$

Question 15

A compound contains $$40.0\%$$ carbon, $$6.7\%$$ hydrogen, and $$53.3\%$$ oxygen by mass. What is its empirical formula?

Accepted Answer

$$CH_2O$$

Question 16

Which of the following is a correct mole-to-mole ratio for the reaction: $$2H_2 + O_2$ \rightarrow 2H_2O$$?

Accepted Answer

$$2\ mol\ H_2$ : 1\ mol\ O_2$

Question 17

Which of the following is a transition metal?

Accepted Answer

Iron

Question 18

Which of the following is a polyatomic ion?

Accepted Answer

$$NO_3$$^-$$

Question 19

A student needs to convert $$250\ mg to $$grams using the factor-label method. Which of the following is correct?

Accepted Answer

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

Question 20

Which of the following best describes a metalloid?

Accepted Answer

An element with properties intermediate between metals and nonmetals

General Chemistry Study Guide: Matter, Measurement, and Chemical Quantities

Guida di studio - Domande di pratica

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