# Chemistry and Environmental Sciences

**Medgar Evers College Prof: Dr. Skeete**

**Chemistry and Environmental Sciences**

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*Show all calculations*

__10__

**Name: __________________________**

__HOMEWORK ASSIGNMENT__

1. For each of the following numbers, underline the zeroes that are significant and draw an *x* through those zeroes that are not.

a. 0.0000000005

b. 0.009090

c. 0.0068

d. 450,802

2. The following numbers are displayed on a calculator. Round off each to four significant figures.

a. 342.985318

b. 0.009650901

c. 3.52569241 x 10-8

d. 1,127,436,092

3. Each of the following numbers was supposed to be rounded to two significant figures. Find the ones that were incorrectly rounded and correct them.

a. 42.3492 to 42.4

b. 3.999 x 102 to 40

c. 0.009964 to 0.010

d. 56.9971 to 57.0

e. 1.249 x 103 to 1.3 x 103

4. Calculate the answer to the correct number of sig.fig.

2.30 ÷ 0.0052330

5. A sample of an unknown metal has a mass of 35.4 g and a volume of 3.11 cm3. Calculate the density of this metal.** **

6. Perform the following calculations to the correct number of significant figures.

a. 4.5 x 0.03060 x 0.391

b. 5.55 ÷ 8.97

c. 7.890 x 1012 ÷ 6.7 x 104

d. 67.8 x 9.8 ÷ 100.04

e. 4.005 x 74 x 0.007

7. A flask that weighs 835.8 g is filled with 225 mL of carbon tetrachloride. The weight of the flask and carbon tetrachloride is found to be 603.55 g. From this information, calculate the **density** of carbon tetrachloride.

8. Find the mass of 350.0 mL of benzene. The density of benzene is 0.8765 g/mL.

9. Write above the number the amount of significant figures it contains and then these numbers into scientific notation.

**2**

(a) 0.00034 , **3.4 x 10-4** (b) 0.002 (c) 40,050,000

(d) 549 (e) 0.0000000082 (f) 0.07514000

(g) 0.04280 (h) 3,621.471 (i) 7,000,631

10. Perform the following calculations to the correct number of significant figures.

a. 87.6 + 9.888 + 2.3 + 100.77

b. 43.7 – 2.341

c. 89.6 +98.33 – 4.674

d. 6.99 – 5.772

11. Take these numbers out of scientific notation and write them as standard numbers.

(a) 9.481 x 10-8 (b) 3.64 x 104 (c) 3.92000 x 102

(d) 8.673 x 10-7 (e) 9.5000 x 100 (f) 5.9267 x 10-1

12. The answer to the multiplication of **0.002780 x 5** reported to the correct number of significant figures is:

13. **Convert the following**: *Show all the steps involved*

(a) 300.0 K to:

i. 0F

ii. 0C

(b) 50.0 0F to 0C

(c) 20.0 0C to 0F

14. What volume of silver metal will weigh exactly 5.30g. The density of silver is 10.5 g/cm3.

15. A running track measures 0.250 mi per lap. To run 10.0 km, how many laps should you run:(Hint: 0.6214 mi = 1 km)

16. Please solve the following conversion problems. (*show all the steps*)

(a) 0.75 kg to milligrams

(b) 825000 millimeters to km

(c) 2.0 pounds to grams

(d) 1.92 km to centimeters

17. Which distance is shorter, 5.0 inches or 5 centimeters.

18. Identify the number of significant figures in the following table.

Number |
Significant Figures |

0.00058790 | |

10 | |

0.10101010 | |

3.50 x 10-5 | |

8,200,000 | |

0.00300 | |

201 | |

500 | |

5001 | |

2.60 x 102 |

**Sorry, no more questions for now.**