Q: If 0.85% of the mass of a human body is potassium, how many kilograms of potassium are in a 150-pound person? (1 kg = 2.2 lb)

$$150 \div 2.2 \times 0.0085 = 0.58 kg$$

Q: How many atoms of silver are in a coin made of pure silver (atomic number 47) and weighing 3.00 g? (Show your work.)

$$3.00 \div 107.9 \times 6.02 \times 10$$^{23}$$ = 1.68 \times 10$$^{22}$$ atoms

Q: A spider produces 0.025 g of venom, injected into 200 mice weighing an average of 0.75 oz each. Half of the mice die. What is the LD$$_{50} in g/kg$$?

$$0.025 \div (200 \times 0.75 \div 35.2) = 0.047 g/kg$$

Question 1

A laboratory technician needs to prepare 75.0 g of benzene (C$$_6H$_6) at 25$^	ext{o}C. If $$the density of benzene is 0.879 g/mL, how many milliliters should be measured out?

Accepted Answer

$$75.0 \div 0.879 = 85.4 mL$$

Question 2

Which of the following readings from a Celsius thermometer is correctly reported with significant figures?

Accepted Answer

18.5$$^	ext{o}C$$

Question 3

If the target is the bullseye, which diagram represents poor accuracy but good precision?

Accepted Answer

(b)

Question 4

If 0.85% of the mass of a human body is potassium, how many kilograms of potassium are in a 150-pound person? (1 kg = 2.2 lb)

Accepted Answer

$$150 \div 2.2 	imes 0.0085 = 0.58 kg$$

Question 5

How many significant figures are in the result of $$5.42 - 17.34 - 2.1$$?

Accepted Answer

One

Question 6

How many significant figures are in the result of $$(0.001 	imes 3.00) \div 2.54$$?

Accepted Answer

One

Question 7

Convert 104$$^	ext{o}F to $$Celsius. (Show your work.)

Accepted Answer

$$(104 - 32) \div 1.8 = 40^	$$ext{o}$C

Question 8

Convert 25 nm to meters.

Accepted Answer

$$25 	imes 10$$^{-9}$$ m

Question 9

At room temperature, an element is a dull, brittle solid that does not conduct electricity. It is most likely a:

Accepted Answer

nonmetal

Question 10

Which element is most chemically similar to the element indicated by X in the periodic table below?

Accepted Answer

Na

Question 11

The shaded group on the periodic table represents:

Accepted Answer

Alkaline earth metals

Question 12

Mendeleev originally arranged the periodic table primarily by:

Accepted Answer

element weight and chemical properties

Question 13

How many atoms of silver are in a coin made of pure silver (atomic number 47) and weighing 3.00 g? (Show your work.)

Accepted Answer

$$3.00 \div 107.9 	imes 6.02 	imes 10$$^{23}$$ = 1.68 	imes 10$$^{22}$$ atoms

Question 14

Which of the following is the correct ranking of atomic radius?

Accepted Answer

K \u003e Ca \u003e Cl

Question 15

Order the following elements by increasing effective nuclear charge (Z$$_{	ext{eff}}$$): O, F, Na, Ne.

Accepted Answer

Na \u003c O \u003c F \u003c Ne

Question 16

Which orbital-filling diagram represents the anomalous ground state of copper?

Accepted Answer

$$[Ar] 4s^1$ 3d$$^{10}$$

Question 17

For a 5d orbital, what are the possible values of $$n$$ and $$l$$?

Accepted Answer

$$n = 5, l = 2$$

Question 18

Which of the following is NOT a valid quantum number set?

Accepted Answer

$$n = 1, l = 1, m_l = 0, m_s = -\frac{1}{2}$$

Question 19

Arrange the following in order of increasing wavelength: ultraviolet, infrared, microwave, visible.

Accepted Answer

ultraviolet \u003c visible \u003c infrared \u003c microwave

Question 20

A spider produces 0.025 g of venom, injected into 200 mice weighing an average of 0.75 oz each. Half of the mice die. What is the LD$$_{50} in g/kg$$?

Accepted Answer

$$0.025 \div (200 	imes 0.75 \div 35.2) = 0.047 g/kg$$

CHEM 121 Principles of Chemistry: Practice Midterm II Study Guide

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