The Law of Conservation of Mass: Mass cannot be ______________ or ______________.

Unit 10 Study Guide: Chemical Equations & Conservation of MassName: Class Period:

Law of Conservation of Mass

Algebra Review:3g + ?g = 9.5g 3.1g + 8.2g = ?g 4g + ?g = 12.4g 8.2g + 17.3g = ?g

1. ? = _____ 2. ? = _____ 3. ? = _____ 4. ? = _____

3.2g + ?g = 7.4g + 4.5g 5.1g + 3.8g = ?g + 6.3g 6.7g + ?g = 9.4g + 10.7g5. ? = _____ 6. ? = _____ 7. ? = _____

8. In a chemical equation, the left side of the equation is known as the ___________________.

9. The right side of the equation is known as the ___________________.

The number of atoms of each element must remain the same before and after a reaction in order for mass of the products to be the same as the mass of the reactants

10. SO THE __________ OF THE REACTANTS MUST EQUAL THE ___________ OF THE PRODUCTS!

hydrogen + oxygen water 8 g 64 g ? g

11. 8 grams of hydrogen reacts with 64 grams of oxygen. Assuming all of the reactants are used up, how much water will be produced? _____________

12. If 64 g of sulfur react with 4 g of oxygen gas, what will be the mass of the sulfur dioxide produced? ______________

2Cu + O2 → 2CuO13. When 127 g of copper reacts with 32 g of oxygen gas to form copper (II) oxide, no copper or oxygen is left over. How much copper (II) oxide is produced?

A 32 g B 95 g C 127 g D 159gmercury(II) oxide oxygen mercury 30.0 g 2.1 g + ? g

14. According to the law of conservation of mass, how much mercury was present in the mercury (II) oxide?

A 30 g B 32.1 g C 27.9 g D 63 g15. According to the law of conservation of mass, how much zinc was present in the zinc carbonate pictured here?

S8 + 8O2 8SO2

Same word here

Unit 10 Study Guide: Chemical Equations & Conservation of MassName: Class Period:

16. Liquid 1 and Liquid 2 react to produce a solid and a gas. Which of the following expressions correctly shows how to determine the mass of the gas?

F (mass of Liquid 1 + mass of Liquid 2) − (mass of solid)G (mass of Liquid 1 + mass of Liquid 2) + (mass of solid)H (mass of Liquid 1 × mass of Liquid 2) ÷ (mass of solid)J (mass of Liquid 1 − mass of Liquid 2) ÷ (mass of solid)

17. Copper (Cu) and sulfur (S) were heated in a covered container. After the reaction was complete, the unreacted sulfur was removed. The table contains the results of the investigation. How much sulfur, in grams, failed to react with the copper? Record your answer to the nearest hundredth.

CaCO3 CaO + CO218. The chemical equation shows CaCO3 being heated. Which of these statements best describes the mass of the products if 100 g of CaCO3 is heated?

A The difference in the products’ masses is equal to the mass of the CaCO3.B The sum of the products’ masses is less than the mass of the CaCO3.C The mass of the each product is equal to the mass of the CaCO3.D The sum of the products’ masses equals the mass of the CaCO3.

19. When 50 mL of isopropyl alcohol (39.5 g) is added to 50 mL of water (50 g), the mixture will have a volume of 98 mL. What is the mass in grams of this mixture? Record and bubble in your answer to the nearest tenth on the answer document.

COEFFICIENTS AND BALANCINGWrite how many of each substance are present after the coefficient has been added:

20. 2CCl4 = ___C + ___Cl 3H2O = ___H + ___O 2O2 = ___O

21. 4SF6 = ___S + ___F 2Fe2O3 = ___Fe + ___O 4 (NH4)2S ___N + ___H + ___ S

22. 3 Si(SO4)4 = ___Si + ___S +___O 6 Mg3(PO4)2 = ___Mg + ___P + ___O

23. DOES THE EQUATION BELOW OBEY THE LAW OF CONSERVATION OF MASS? ________

Br2 + 2NaI 2NaBr + I2

___ Br ___ ___ Na ___ ___ I ___

Use the blanks to keep track of how many of each

element is on each side!

Unit 10 Study Guide: Chemical Equations & Conservation of MassName: Class Period:

24. Which chemical equation supports the law of conservation of mass?

A. 2H2O(l) → H2(g) + O2(g) B. Zn(s) + HCl(aq) → ZnCl2(aq) + H2(g)

C. Al4C3(s) + H2O(l) → CH4(g) + Al(OH)3(s) D. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

Carbon Monoxide (CO) burns readily in Oxygen (O2) to form carbon dioxide (CO2)

__ CO + __ O2 → __ CO2

25. What coefficient values will balance the reaction shown above? (Show your work, counting atoms for each set of coefficients.)

A 2, 2, 1 B 1, 1, 1 C 2, 1, 2 D 1, 2, 2

26. Aluminum metal and oxygen gas combine to produce aluminum oxide (Al2O3). Which of these is the balanced equation for this reaction?

F Al + O2 → Al2O3 G 2Al + 2O2 → 2Al2O3

H 2Al + 3O2 → 5Al2O3 J 4Al + 3O2 → 2Al2O3

H2 + O2 H2O27. What coefficient values will balance the reaction shown above? (Show your work for each set of coefficients.)

A 2, 1, 1 B 2, 1, 2 C 1, 1, 1 D 2, 1, 1N2 + H2 NH3

28. What coefficient values will balance the reaction shown above? (Show your work for each set of coefficients.)

A 2, 2, 1 B 1, 3, 1 C 1, 3, 2 D 1, 1, 1

C + H2 + O2 C2H6O29. What coefficient values will balance the reaction shown above? (Show your work for each set of coefficients.)A 2, 2, 1, 1 B 4, 6, 1, 1 C 1, 3, 2, 2 D 4, 6, 1,

2

____H____ ____O____

____Zn____ ____Cl____ ____H____

___Al___ ___C___ ___H___ ___O___

____C____ ____H____ ____O____

Make your own tables to keep track of the aluminums and oxygens and check each answer choice!

Unit 10 Study Guide: Chemical Equations & Conservation of MassName: Class Period:

The next question can be done exactly the same way, except that instead of plugging in coefficients, you plug in substances with their coefficients. Use

your tables to see which comes out to be balanced!

30. Which additional product balances this reaction?F 4OH(aq) G CH4(g) H H2O2(g) J 2H2O(g)

Sometimes they will require you to start from scratch and balance an equation on your own. There are some tricks to getting started:

● Look at both sides of the equation to find an element that has a different amount on each side.

● If you see an element with an odd numbered subscript, start by putting a 2 in front of it. (This

won’t always work, but it works often enough to be used if you struggle with balancing.)

Balance the following equations:

32. ______N2 + ______H2 ______NH3

33. ______H2O ______H2 + ______O2

PbO2 PbO + O2

31. What are the coefficients that will balance this chemical equation?

A 2, 1, 1B 3, 4, 2C 2, 2, 1D 4, 3, 2

Make your own tables to keep

track of the lead (Pb) and oxygen (O) and check each answer

choice!

Mg + HCl MgCl2 + H2

34. When the above equation is balanced, the coefficient for magnesium chloride is -

A 0 B 1 C 2 D 4

K + H2O KOH + H2

35. What is the coefficient for H2O when the above equation is balanced?

A 1 B 2 C 3 D 4

Unit 10 Study Guide: Chemical Equations & Conservation of MassName: Class Period:Less often, you use ratios of balanced equations to draw conclusions. This is simple, so lets cover it to make sure you can do it. Use the equation for photosynthesis for all of the problems below.

40.

41.

Photosynthesis:6CO2 + 6H2O C6H12O6 + 6O2

36. To produce 4 molecules of sugar, a plant needs – A 6 molecules of hydrogenB 12 molecules of ATPC 18 molecules of waterD 24 molecules of carbon dioxide

37. To produce 18 molecules of oxygen, a plant needs – A 6 molecules of sugarB 12 molecules of ATPC 18 molecules of waterD 12 molecules of carbon dioxide

38. If a plant reacts 12 molecules of carbon dioxide, it will produce – A 2 molecules of sugarB 12 molecules of ATPC 24 molecules of waterD 18 molecules of oxygen

39. If a plant reacts 24 molecules of water, it will produce – A 3 molecules of sugarB 6 molecules of ATPC 18 molecules of carbon dioxideD 24 molecules of oxygen

Unit 10 Study Guide: Chemical Equations & Conservation of MassName: Class Period:42.

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Unit 10 Study Guide: Chemical Equations & Conservation of MassName: Class Period:47.

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Unit 10 Study Guide: Chemical Equations & Conservation of MassName: Class Period:50. If you represent hydrogen with triangles, oxygen with circles and calcium with squares, draw a model of the following reaction: H2O + Ca --> H2 + CaO.

PaP bonuses: +1 What effect does having 8 valence electrons have on atoms?

+2 How do the oceans deliver most of the energy they have absorbed from the sun into the atmosphere to form storms such as hurricanes?

+3 Explain why heated air rises.