Q: A student needs to prepare 250 mL of a 0.2 M NaCl solution from solid NaCl. The molar mass of NaCl is 58.44 g/mol. How many grams of NaCl are required?

$$0.2 \times 0.250 \times 58.44 = 2.92 g$$

Q: Which of the following is the correct formula to calculate the molarity ($$M) of a $$solution?

$$M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}$$

Q: Given $$[H^+] = 1 \times 10$$^{-5}$$ M, what is the pH of the solution?

$$pH = -\log_{10}(1 \times 10$$^{-5}$$) = 5$$

Question 1

Which of the following best describes a continuous random variable?

Accepted Answer

A variable that can take any value within a given range, such as the mass of a chemical sample measured in grams.

Question 2

You are asked to measure 25.0 mL of a liquid as accurately as possible. Which instrument should you use?

Accepted Answer

A 25 mL graduated cylinder

Question 3

A student needs to prepare 250 mL of a 0.2 M NaCl solution from solid NaCl. The molar mass of NaCl is 58.44 g/mol. How many grams of NaCl are required?

Accepted Answer

$$0.2 	imes 0.250 	imes 58.44 = 2.92 g$$

Question 4

Which of the following is the correct formula to calculate the molarity ($$M) of a $$solution?

Accepted Answer

$$M = \frac{	ext{moles of solute}}{	ext{volume of solution in liters}}$$

Question 5

A student is preparing a serial dilution by transferring 1 mL of a stock solution into 9 mL of water, mixing, and repeating this process three times. What is the final dilution factor after the third dilution?

Accepted Answer

$$10^3 = 1000$

Question 6

If the absorbance of a solution is 0.45 and the trendline equation from a calibration curve is $$y = 0.25x + 0.05$$, where $$y is $$absorbance and $$x is $$concentration in M, what is the concentration of the solution?

Accepted Answer

$$x = \frac{0.45 - 0.05}{0.25} = 1.6 M$$

Question 7

Which of the following best describes a buffer solution?

Accepted Answer

A solution that resists changes in pH when small amounts of acid or base are added.

Question 8

Given $$[H^+] = 1 	imes 10$$^{-5}$$ M, what is the pH of the solution?

Accepted Answer

$$pH = -\log_{10}(1 	imes 10$$^{-5}$$) = 5$$

Question 9

Which of the following statements correctly distinguishes prokaryotic from eukaryotic cells?

Accepted Answer

Prokaryotic cells lack membrane-bound organelles, while eukaryotic cells contain them.

Question 10

Why is it necessary to add dye to cells when viewing them under a light microscope?

Accepted Answer

Most cells are transparent and dyes increase contrast, making structures visible.

Question 11

A dialysis bag containing a 10% sucrose solution is placed in a beaker of pure water. What will happen to the bag over time?

Accepted Answer

Water will enter the bag by osmosis, causing it to swell.

Question 12

Which of the following best explains the difference between dialysis tubing and a living cell membrane?

Accepted Answer

Dialysis tubing is selectively permeable based on size, while living membranes are selectively permeable based on size and specific transport proteins.

Question 13

Which of the following is the correct way to tare a balance before weighing a sample?

Accepted Answer

Place the empty container on the balance and press the tare button to zero the display.

Question 14

A student is asked to convert 250 mL to liters. What is the correct conversion?

Accepted Answer

$$250 	ext{ mL} 	imes \frac{1 	ext{ L}}{1000 	ext{ mL}} = 0.250 	ext{ L}$$

Question 15

Which of the following is a correct statement about the domains of life?

Accepted Answer

Domain Archaea and Domain Bacteria both contain prokaryotic organisms.

Question 16

A solution has a pH of 3. What is the hydrogen ion concentration $$[H^+]$$?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-3}$$ M

Question 17

Which of the following best describes the net movement of water during osmosis?

Accepted Answer

Water moves from an area of low solute concentration to an area of high solute concentration.

Question 18

When focusing a slide under a compound light microscope, what is the correct sequence of steps?

Accepted Answer

Start with the lowest power objective, use coarse focus to bring the specimen into view, then switch to higher power and use fine focus.

Question 19

A student observes that a dye diffuses faster in 1% agar at 37°C than in 3% agar at 4°C. Which factor(s) best explain this observation?

Accepted Answer

Both lower agar concentration and higher temperature increase the rate of diffusion.

Introductory Chemistry Lab Skills and Concepts: Study Guide

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