Chapter 3 Unit Review 1. You have a 78 g sample of a compound of which 12.4 g is hydrogen. What is the % by mass of hydrogen in the sample?

2. A sample is made-up of 1 g hydrogen and 19 g fluorine. What is the % by mass of hydrogen in the sample.

3. When 3.5 g of X reacts with 10.5 g Y to form a compound of XY, what is the % by mass of X in this sample? What is the % by mass of Y is this sample?

4. Two different compounds made up of the same elements but is different proportions, (different masses) is governed by what Law: ans: Law of Multiple Proportions

5. Given two compounds. Compound one has 15g hydrogen and 120 g oxygen. Compound two has 2 g hydrogen and 32 g oxygen. Are the two compounds the same?

6. You have a sample compound made up of g magnesium and 6.96 g oxygen, what is the % by mass of oxygen in the sample?

7. Compound one: 4.82 g carbon and 6.44 g oxygen. Compound two: g carbon and 53.7 g oxygen. What is the ratio of the 2 compounds?

8. Compound one: 6.46 g lead and 1 g oxygen. Compound two: g lead and g oxygen. Are the two compound the same?

9. Compound one: g chlorine and g fluorine. What is the % by mass of chlorine? What is the % by mass of fluorine?

10. Given 20 g sample of sucrose g carbon, 1.30 g hydrogen and g oxygen. What is the % by mass of each element?

11. Given a 500 g sample of an unknown that contains 32.5 g hydrogen, g oxygen and an unknown amount of carbon. Is the compound sucrose? Look at #10.

12. Given N 2 + 3H 2  2NH 3 with 28 g nitrogen and 6 g hydrogen, what is the mass of NH 3 ?

Any additional problems?

13. Are the following physical or chemical properties? Conducts electricity Boils at 85 o C Colorless Remains unchanged when reacting with oxygen Liquid at room temperature Condensing Vaporizing Exploding Fermentation Tarnishing Grinding

14. Are the following heterogeneous mixtures or homogeneous mixtures? Alloy wheels Salad dressing Pizza Air Salt water Blood Concrete mix

15. Identify each as true or false: Solids have a defined shape and volume? Density for the same matter is always the same? Density is an extensive physical property? Transfer of energy indicates a chemical change? Latex paint is a heterogeneous mixture? Solutions are all homogeneous mixtures? Water contracts when heated? Gas production indicates a physical change?

16. Is it a chemical or physical change when ice melts to water? ans: physical 17. Is mass and length of an object intensive or extensive physical properties? ans: extensive 18. Is energy in or energy out required for a liquid to freeze? ans: energy out

19. Is distillation a chemical or physical changing process? ans: physical 20. What is the physical state of matter that has a defined volume with no defined shape? ans: liquid 21. The separation of a mixture by passing the mixture through a semi-permeable membrane is called ______________ ans: filtration

22. Matter is neither created nor destroyed but can change in form, is what Law? ans: Law of the Conservation of Matter 23. The combination of two or more elements is called a (n) : ans: compound 24. A gas that normally exists as a liquid at room temperature is called a(n) : ans: vapor

25. Two elements combine in a fixed ration by mass is called: ans: Law of Definite Proportions 26. Different compound can be formed from the same elements in different proportions by mass as long as the ratio between the two compounds are a small whole number? ans: Law of Multiple Proportions 27. Matter that has a uniform and unchanging composition is ans: a substance