Homework #1


Homework is due in class by the date indicated above. Late homework will be docked significantly.

Q1

Complete each calculation with the correct number of significant figures

1. $$\dfrac{7.68 \times 8.009}{4.1}\phantom{\dfrac{\Big(}{\Big(}}$$
2. $$\dfrac{6.89-5.452}{1.596+4.7121}\phantom{\dfrac{\Big(}{\Big(}}$$
3. $$\dfrac{3.668\times10^{-7}+ 8.3469\times10^{-7}}{3.7348\times10^{-10}}\phantom{\dfrac{\Big(}{\Big(}}$$

Q2

Calculate how many grams of mixture are there if 250 mL of ethanol is mixed with 500 mL of benzene.

 Substance Density (g/cm3) Ethanol 0.789 Benzene 0.880

Q3

Give the ISOTOPIC symbol for the following ions:

1. Ion with 73 Protons, 75 Electrons, and 107 Neutrons.
2. Ion with 28 Protons, 25 Electrons, and 31 Neutrons
3. Ion with 37 Protons, 37 Electrons, and 49 Neutrons
4. Ion with 7 Protons, 7 Electrons, and 7 Neutrons

Q4

Label the following elements as halogens, alkali metals, alkaline earth metals, noble gases, or transition metals.

1. Lithium,
2. Chlorine
3. Argon
4. Krypton
5. Calcium
6. Barium
7. Cesium
8. Fluorine
10. Tungsten

Q5

An element consists of the following isotopes. What is the average atomic mass and the name of the element?

 Percent natural abundance Mass (u) 90.48% 19.9924 0.27% 20.9938 9.25% 21.9914

Q6

A compound, made only from mercury and sulfur, is 86.2% $$Hg$$ by mass. The molar mass of this compound is 465 g/mol. Determine the empirical formula and the molecular formula of this compound.

Q7

A compound is a common first-aid antiseptic. The products of its combustion reaction in the presence of oxygen gas are water and carbon dioxide. This compound is composed of carbon, hydrogen and oxygen. If 9.214 g of this compound produces 17.604 g carbon dioxide and 10.812 g water, what is the empirical formula of this compound? Hint: Some oxygen atoms of the products may come from oxygen gas.

Q8

Assign the oxidation state of each atom for the following compounds.

1. $$Al$$
2. $$PbSO_4$$
3. $$H_2SO_3$$
4. $$NaHCO_3$$
5. $$H_2O_2$$
6. $$Ne$$
7. $$MgCO_3$$
8. $$Na_2Cr_2O_7$$

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