Q: If the concentration of hydrogen ions in a solution is $$[H^+] = 1 \times 10$$^{-4}$$\ mol/L$$, what is the pH?

$$pH = -\log(1 \times 10$$^{-4}$$) = 4$$

Q: A student needs to dilute a stock solution from $$2\ M to$$ $$0.5\ M$$ using parallel dilution. If the final volume required is $$100\ mL$$, what volume of stock solution should be used?

$$V_1$$ = \frac{$$C_2$$ \times $$V_2$$}{$$C_1$$} = \frac{0.5\ M \times 100\ mL}{2\ M} = 25\ mL$$

Question 1

Which of the following is an example of a continuous random variable in a chemistry lab?

Accepted Answer

The mass of a sample measured on a balance

Question 2

You are asked to measure the volume of a liquid with high precision. Which instrument should you use?

Accepted Answer

Graduated cylinder

Question 3

A solution is prepared by dissolving 10 g of NaCl in enough water to make 500 mL of solution. What is the molarity ($$M) of $$the solution? (Molar mass of NaCl = $$58.44\ g/mol)$$

Accepted Answer

$$M = \frac{10\ g}{58.44\ g/mol} \div 0.5\ L = 0.342\ M$$

Question 4

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 5

If the concentration of hydrogen ions in a solution is $$[H^+] = 1 	imes 10$$^{-4}$$\ mol/L$$, what is the pH?

Accepted Answer

$$pH = -\log(1 	imes 10$$^{-4}$$) = 4$$

Question 6

A student needs to dilute a stock solution from $$2\ M to$$ $$0.5\ M$$ using parallel dilution. If the final volume required is $$100\ mL$$, what volume of stock solution should be used?

Accepted Answer

$$V_1$$ = \frac{$$C_2$$ 	imes $$V_2$$}{$$C_1$$} = \frac{0.5\ M 	imes 100\ mL}{2\ M} = 25\ mL$$

Question 7

Which of the following statements about prokaryotic cells is TRUE?

Accepted Answer

Prokaryotic cells lack a nucleus

Question 8

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

Accepted Answer

To make cell structures more visible by increasing contrast

Question 9

A dialysis bag containing a concentrated sugar solution is placed in pure water. What will happen?

Accepted Answer

Water will move into the bag by osmosis

Question 10

Which SI unit would you use to measure the length of a cell under a microscope?

Accepted Answer

Micrometer ($$\mu m)$$

Question 11

You are given a graph of absorbance vs. concentration for a solution. The trendline equation is $$y = 0.8x + 0.05$$, where $$y is $$absorbance and $$x is $$concentration. If the measured absorbance is $$0.45$$, what is the concentration?

Accepted Answer

$$x = \frac{0.45 - 0.05}{0.8} = 0.5$$

Question 12

Which of the following is NOT a basic safety guideline in the laboratory?

Accepted Answer

Eating and drinking in the lab

Question 13

What is the correct procedure for taring a balance before measuring the mass of a sample?

Accepted Answer

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

Question 14

Which domain includes organisms with membrane-bound organelles?

Accepted Answer

Domain Eukarya

Question 15

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

Accepted Answer

$$250\ mL = 0.25\ L$$

Question 16

Which of the following best describes the difference between serial and parallel dilutions?

Accepted Answer

Serial dilutions involve diluting a solution stepwise, each step using the previous dilution; parallel dilutions use the stock solution for each dilution

Question 17

Which of the following is a discrete random variable?

Accepted Answer

The number of bubbles formed in a reaction

Question 18

Which part of the microscope is used to adjust the focus at high magnification?

Accepted Answer

Fine focus knob

Question 19

A student observes that dye diffuses faster in agar at $$37^\circ C$$ than at $$20^\circ C. $$Which principle best explains this observation?

Accepted Answer

Diffusion rate increases with temperature due to increased molecular motion

Introductory Chemistry Lab Skills and Concepts: Study Guide

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