Q: A 225 g sample of water is heated from 25.0 °C to 100.0 °C. How much heat (in joules) is required? (Specific heat of water = $$4.184 \ \mathrm{J/g\ ^\circ C})$$

$$q = 225 \times 4.184 \times (100.0 - 25.0) = 70,530 \ \mathrm{J}$$

Question 1

Which property of water explains why ice floats on liquid water?

Accepted Answer

Water expands when it freezes, making ice less dense than liquid water.

Question 2

Which equation correctly represents the amount of heat required to raise the temperature of a substance?

Accepted Answer

$$q = mC\Delta T$$

Question 3

A 225 g sample of water is heated from 25.0 °C to 100.0 °C. How much heat (in joules) is required? (Specific heat of water = $$4.184 \ \mathrm{J/g\ ^\circ C})$$

Accepted Answer

$$q = 225 	imes 4.184 	imes (100.0 - 25.0) = 70,530 \ \mathrm{J}$$

Question 4

Which of the following best describes why water is called the 'universal solvent'?

Accepted Answer

Water can dissolve a wide variety of substances due to its ability to hydrogen-bond.

Question 5

Which of the following is a natural contaminant in water that can cause hard water?

Accepted Answer

Calcium and magnesium salts

Question 6

What is the main environmental effect of acid rain?

Accepted Answer

It lowers the pH of soil, lakes, and streams, causing environmental damage.

Question 7

Which process in the water cycle is responsible for the movement of water from the surface to the atmosphere?

Accepted Answer

Evaporation

Question 8

A sample of seawater contains $$3.90 	imes 10$$^{-6}$$ ppm of dissolved gold. How many liters of seawater are needed to obtain 1.00 g of gold? (Assume density of water is 1.00$$ \ \mathrm{g/mL}$$)

Accepted Answer

$$2.56 	imes 10^8$ L

Question 9

Which of the following is a major health risk associated with nitrate contamination in groundwater?

Accepted Answer

Methemoglobinemia (blue baby syndrome)

Question 10

What is the primary purpose of adding slaked lime and alum during water treatment?

Accepted Answer

To coagulate and remove colloidal particles and bacteria

Question 11

Which chemical reaction represents the formation of aluminum hydroxide during water treatment?

Accepted Answer

$$3 \ \mathrm{Ca(OH)_2(aq)} + \mathrm{Al_2$(SO_4$)_3(aq)} \rightarrow 2 \ \mathrm{Al(OH)_3(s)} + 3 \ \mathrm{$$CaSO_4$$(aq)}$$

Question 12

Which of the following statements about water disinfection is correct?

Accepted Answer

Chlorine is commonly used because it provides residual protection against bacteria.

Question 13

What is the chemical reaction that occurs when fluoride is added to tooth enamel?

Accepted Answer

$$\mathrm{Ca_5$(PO_4$)_3OH(s)} + \mathrm{F^-(aq)} \rightarrow \mathrm{Ca_5$(PO_4$)_3F(s)} + \mathrm{OH^-(aq)}$$

Question 14

Which of the following is a disadvantage of using ultraviolet (UV) light for water disinfection?

Accepted Answer

It does not provide residual protection after treatment.

Question 15

Which of the following is a secondary (nonenforceable) standard for drinking water according to the EPA?

Accepted Answer

Chloride ion

Question 16

What is the main purpose of secondary sewage treatment?

Accepted Answer

To allow aerobic bacteria to break down organic matter

Question 17

Which of the following best describes eutrophication in lakes?

Accepted Answer

A process where lakes age and accumulate nutrients, often accelerated by human activity

Question 18

Which of the following is a real-world consequence of excessive fluoride in drinking water?

Accepted Answer

Dental fluorosis, which causes discoloration of teeth

Question 19

Which of the following is a correct definition of 'parts per million' (ppm)?

Accepted Answer

$$1 \ \mathrm{g}$$ solute per $$10^6$$ \ \mathrm{g}$$ solution

Water: Properties, Contamination, and Treatment (Introductory Chemistry Study Notes)

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