Q: A chemist reacts $10.0\ g$ of calcium metal with excess water and collects $5.00\ g$ of calcium hydroxide. Using the equation $\mathrm{Ca(s) + 2\ H_2O(l) \rightarrow Ca(OH)_2(aq) + H_2(g)}$, what is the percent yield?

$\text{Percent yield} = \frac{5.00\ g}{18.5\ g} \times 100\% = 27.1\%$

Q: Calculate the percentage by mass of carbon in $\mathrm{CO_2}$.

$\frac{12.01}{44.01} \times 100\% = 27.29\%$

Question 1

Which of the following compounds is most likely to conduct electricity when dissolved in water, and why?

Accepted Answer

CaO, because it is an ionic compound that dissociates into ions.

Question 2

A patient’s body temperature is measured at 37°C. What is this temperature in Kelvin?

Accepted Answer

$K = 37 + 273.15 = 313\ K$

Question 3

Titanium metal melts at $1672\ ^\circ C$. What is its melting point in Kelvin?

Accepted Answer

$K = 1672 + 273 = 1945\ K$

Question 4

A chemist reacts $10.0\ g$ of calcium metal with excess water and collects $5.00\ g$ of calcium hydroxide. Using the equation $\mathrm{Ca(s) + 2\ H_2O(l) \rightarrow Ca(OH)_2(aq) + H_2(g)}$, what is the percent yield?

Accepted Answer

$	ext{Percent yield} = \frac{5.00\ g}{18.5\ g} 	imes 100\% = 27.1\%$

Question 5

Calculate the percentage by mass of carbon in $\mathrm{CO_2}$.

Accepted Answer

$\frac{12.01}{44.01} 	imes 100\% = 27.29\%$

Question 6

Which of the following is the correct formula and charge for the carbonate ion?

Accepted Answer

$\mathrm{CO_3^{2-}}$

Question 7

A sample of osmium has a mass of $21.8\ g$ and a density of $22.6\ g/cm^3$. What is its volume?

Accepted Answer

$V = \frac{21.8\ g}{22.6\ g/cm^3} = 0.965\ cm^3$

Question 8

Which of the following reactions is a decomposition reaction?

Accepted Answer

$\mathrm{NH_4Cl \rightarrow NH_3 + HCl}$

Question 9

How many grams of silver chloride ($\mathrm{AgCl}$, $143.32\ g/mol$) are formed when $10.0\ g$ of silver nitrate ($\mathrm{AgNO_3}$, $169.87\ g/mol$) reacts with $15.0\ g$ of barium chloride ($\mathrm{BaCl_2}$, $208.23\ g/mol$) according to $2\mathrm{AgNO_3} + \mathrm{BaCl_2} \rightarrow 2\mathrm{AgCl} + \mathrm{Ba(NO_3)_2}$?

Accepted Answer

$8.44\ g$

Question 10

Which of the following are chemical changes?

Accepted Answer

1. Rusting of a nail; 3. Decomposition of water into hydrogen and oxygen gases

Question 11

Which of the following numbers has the greatest number of significant figures?

Accepted Answer

$0.5070$

Question 12

A student weighs $3000.\ \mu g$ of sulfur in the lab. What is this mass in nanograms?

Accepted Answer

$3.000 	imes 10^6\ ng$

Question 13

How many protons and neutrons are in an atom of $^{90}_{38}\mathrm{Sr}$?

Accepted Answer

38 protons, 52 neutrons

Question 14

What is the mass of $8.50 	imes 10^{22}$ molecules of ammonia ($\mathrm{NH_3}$)?

Accepted Answer

$2.40\ g$

Question 15

How many grams of calcium chloride ($\mathrm{CaCl_2}$, $110.98\ g/mol$) are needed to produce $10.0\ g$ of potassium chloride ($\mathrm{KCl}$, $74.55\ g/mol$) in the reaction $\mathrm{CaCl_2(aq) + K_2CO_3(aq) \rightarrow 2\ KCl(aq) + CaCO_3(aq)}$?

Accepted Answer

$7.44\ g$

Question 16

What is the molar mass of $\mathrm{Co(NO_3)_2}$?

Accepted Answer

$183\ g/mol$

Question 17

There are ________ oxygen atoms in 30 molecules of $\mathrm{C_{20}H_{42}S_3O_2}$.

Accepted Answer

60

Question 18

Which subatomic particle has the smallest mass?

Accepted Answer

an electron

Question 19

Which of the following is an exact number?

Accepted Answer

2 people

General Chemistry Exam 1 Study Guidance

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