Q: Which of the following is the correct formula for calculating molarity ($$M$$)?

$$M = \dfrac{\text{moles of solute}}{\text{liters of solution}}$$

Question 1

Which of the following best describes the molecular geometry and bond angle of a molecule with the Lewis structure of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

Tetrahedral, $$109.5^\circ$$

Question 2

A student is asked to determine if carbon dioxide ($$\mathrm{CO_2$}) is a $$polar or non-polar molecule. After drawing the Lewis structure and considering the molecular geometry, what is the correct conclusion and why?

Accepted Answer

$$\mathrm{CO_2$} is $$non-polar because it has polar bonds but a linear, symmetrical shape.

Question 3

During the copper cycle experiment, you start with solid copper and react it with concentrated nitric acid. What type of reaction is this, and what is the main product formed?

Accepted Answer

Redox; copper(II) nitrate

Question 4

You are asked to balance the following equation from the copper cycle: $$\mathrm{Cu(s) + 4HNO_3(aq) \rightarrow Cu(NO_3$)_2(aq) + 2NO_2(g) + 2H_2O(l)}. $$What is the coefficient in front of $$\mathrm{$$HNO_3$$}$$?

Accepted Answer

4

Question 5

A student collects $$0.250 L of $$gas over water at $$25^\circC $$and $$1.00$$ atm total pressure. The vapor pressure of water at $$25^\circC is$$ $$0.0313$$ atm. What is the partial pressure of the dry gas collected?

Accepted Answer

$$0.969$$ atm

Question 6

Which equation would you use to calculate the number of moles of a gas collected in the bicarbonate determination lab, and what does each variable represent?

Accepted Answer

$$PV = nRT$$, where $$P is $$pressure, $$V is $$volume, $$n is $$moles, $$R is $$the gas constant, and $$T is $$temperature in Kelvin.

Question 7

If you dilute $$10.0 mL of a$$ $$2.00 M $$NaCl solution to a final volume of $$100.0 mL$$, what is the final concentration?

Accepted Answer

$$0.20 M$$

Question 8

Which piece of equipment would you use to accurately measure and transfer $$5.00 mL of a $$solution during a dilution procedure?

Accepted Answer

Volumetric pipette

Question 9

A student calculates a theoretical yield of $$1.50 g of $$copper but recovers $$1.35 g $$after the experiment. What is the percent recovery?

Accepted Answer

$$90.0\%$$

Question 10

Which of the following best describes the difference between electron geometry and molecular geometry for ammonia ($$\mathrm{NH_3$}$$)?

Accepted Answer

Electron geometry is tetrahedral, but molecular geometry is trigonal pyramidal due to one lone pair.

Question 11

Which of the following is NOT a correct safety practice in the chemistry lab?

Accepted Answer

Tasting chemicals to identify them

Question 12

A solution is tested and found to conduct electricity well and forms a precipitate with silver nitrate. Which type of solution is this most likely to be?

Accepted Answer

A strong electrolyte solution containing chloride ions

Question 13

Which of the following is the correct scientific notation for $$0.000345$$?

Accepted Answer

$$3.45 	imes 10$$^{-4}$$

Question 14

You are asked to prepare $$250 mL of a$$ $$0.100 M $$NaOH solution from a $$1.00 M $$stock solution. What volume of stock solution should you use?

Accepted Answer

$$25.0 mL$$

Question 15

Which of the following best explains why water is a bent molecule rather than linear?

Accepted Answer

Water has two lone pairs on oxygen, causing repulsion and a bent shape.

Question 16

A student needs to convert $$350 mL to $$liters for a calculation. What is the correct value in liters?

Accepted Answer

$$0.350 L$$

Question 17

Which of the following statements about Dalton’s Law of Partial Pressures is correct?

Accepted Answer

The total pressure of a mixture of gases is the sum of the partial pressures of each gas.

Question 18

Which of the following best describes the color and solubility of copper(II) hydroxide formed during the copper cycle experiment?

Accepted Answer

Blue and insoluble

Question 19

A student’s experimental value for the amount of gas collected is $$0.0180$$ mol, but the theoretical value is $$0.0200$$ mol. What is the percent error?

Accepted Answer

$$10.0\%$$

Question 20

Which of the following is the correct formula for calculating molarity ($$M$$)?

Accepted Answer

$$M = \dfrac{	ext{moles of solute}}{	ext{liters of solution}}$$

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