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An enzyme is a special kind of catalyst. How does it work? Show Answer

Answer for 5 Points It speeds up a specific biochemical reaction. Back to Board

What must be true for a substance to be recognized as an element? Show Answer

Answer for 5 Points Be made up of only one type of atom Back to Board

A student set up the apparatus for electrolysis of water and let it run for 5 minutes; she collected 60 cm 3 of hydrogen. What volume of oxygen did she collect? Show Answer

Answer for 5 Points 30 cm 3 Back to Board

What is a synthesis reaction? Show Answer

Answer for 5 Points A chemical reaction that results in the combination of two or more pure substances to make a more complex pure substance. Example: 2H 2 + O 2  2H 2 O Back to Board

Show Answer What is a decomposition reaction?

Answer for 5 Points A chemical reaction that results in the breaking down of pure substance into two or more pure substances Example: 2H 2 O  2H 2 + O 2 Back to Board

Show Answer What is an incomplete reaction?

Answer for 10 Points Neither of the reactants are completely used up in the chemical reaction. Example: 2Cu + O 2  2CuO Back to Board

What is a complete reaction? Show Answer

Answer for 10 Points One of reactants is completely used up, causing the chemical reaction to stop. Example: Zn + 2HCl  ZnCl 2 + H 2 Back to Board

In the Synthesis of Water…. Show Answer Volume H 2 Volume O 2 What’s Left? 75 cm 3 25 cm 3 50 cm 3 25 cm cm cm 3

Answer for 10 Points Back to Board Volume H 2 Volume O 2 What’s Left? 75 cm 3 25 cm 3 25 cm 3 H 2 50 cm 3 25 cm 3 O 2 50 cm 3 25 cm 3 Nothing 150 cm cm 3 25 cm 3 O 2

Describe the Law of constant Proportions- Show Answer

Answer for 10 Points When two substances combine to form a compound, they always combine in a constant proportion. The ratio of the masses that react remains constant, no matter how much of the substances are mixed. It is a Law of nature. Back to Board

Show Answer When doing Experiment 6.2, The Decomposition of Water, a student began with 100 cm 3 of water in the apparatus. The student collected 57 cm 3 3 of hydrogen and 28 cm 3 3 of oxygen. What fraction of the total volume of water was decomposed?

Answer for 10 Points 4.1 x Back to Board

Show Answer What evidence do you have for each of the following statements? a. Zinc chloride is a pure substance and not a mixture. b. Water is a pure substance.

Answer for 15 Points a.The ratio (mass of zinc reacted)/(mass of zinc chloride)is constant, regardless of how much zinc is added to hydrochloric acid b.Water has a definite melting point, so it is not a mixture. When hydrogen and oxygen are mixed in different ratios and ignited, they combine in a fixed ratio and form water. Back to Board

A student heated a crucible containing 2.15 g of powdered copper until the mass of the contents of the crucible became 2.42 g. The black solid in the crucible was then placed in hydrochloric acid, and 1.08 g of copper remained undissolved in the acid. What is the ratio of the mass of oxygen reacted to the mass of copper reacted? Show Answer

Answer for 15 Points Mass of oxygen reacted= 0.27=0.25 Mass of copper reacted 1.07 g Back to Board

Show Answer If two substances react to form a compound, and only one of them remains when the reaction is overl is the reaction complete or incomplete?

Answer for 15 Points Complete Reaction Back to Board

A complete reaction takes place between Substance A and Substance B. What will remain after the reaction? (Select all the possible correct answers.) A. Substance A and the product of the reaction only B. Substance Band the product of the reaction only C. Both Substance A and Substance B1 along with the product of the reaction D. Neither Substance A nor Substance B; all that will be left is the product of the reaction Show Answer

Answer for 15 Points A,B,D Back to Board

An incomplete reaction takes place between Substance A and Substance B. What will remain after the reaction? (Select all the possible correct answers.) A.Substance A and the product of the reaction only B.Substance Band the product of the reaction only C.Both Substance A and Substance B, along with the product of the reaction D.Neither Substance A nor Substance B; all that will be left is the product of the reaction Show Answer

Answer for 15 Points C Back to Board

Show Answer Does the volume of hydrogen plus the volume of oxygen collected in Experiment 6.2 equal the volume of water decomposed?

Answer for 20 Points No Back to Board

Show Answer What is the combined mass of oxygen and hydrogen that can be produced when 180 g of water is decomposed by electrolysis?

Answer for 20 Points The combined mass of oxygen and hydrogen would be same as the mass of water decomposed-180 g mass is conserved Back to Board

Show Answer If all the volume of hydrogen gas produced from a 180 g of water were burned in air to form water, what mass of water would result?

Answer for 20 Points The mass of water produced would be same as the mass of the original sample that was decomposed -180 g Back to Board

Show Answer Suppose that some zinc chloride solution was left in the test tube when the solution was poured into the evaporating dish. How would this affect your calculation for the ratio of the mass of zinc reacted to the mass of chlorine reacted?

Answer for 20 Points The amount of zinc chloride that is evaporated to dryness would be less than it should be. When mass of chlorine reacted is found by subtracting the mass of zinc reacted from the mass of zinc chloride produced, the resulting mass of chlorine will be too small. Since the mass of chlorine is in the denominator of the ratio, this would increase the ration of the mass of zinc reacted to the mass of chlorine reacted. Back to Board

Show Answer a.How much chlorine will react with 5.00 g of zinc to form zinc chloride? b. How much zinc chloride will be produced?

Answer for 20 Points a.If the ratio of zinc to chlorine is 0.92, 5.00 g of zinc will react 5.00/0.92 =5.43 g of Chlorine b.The mass of zinc chloride produced is 5.00 g =10.43 Back to Board

Show Answer

Answer for 25 Points Ratios b, c, d, f,and g are constant Back to Board

Show Answer In the electrolysis ofwater, which of the following conditions affects the ratio of the volume of hydrogen produced to the volume of oxygen produced? A. The time the apparatus was connected to the battery B. The mass of water electrolyzed C. The temperature of the water D. The mass of sodium carbonate added to the water E. None of the above

Answer for 25 Points E. None of the above Back to Board

Show Answer When water is electrolyzed, the volume of hydrogen produced is twice the volume of oxygen produced. The density of hydrogen is 8.4 x 10-5 g/cm3; the density of oxygen is 1.3 x 10-3 g/cm3. On the basis of these data, what is the value of this ratio? Mass of hydrogen in a sample of water Mass of oxygen in the same sample of water

Answer for 25 Points 2 x 8.4 x x 1.3 x Back to Board

Show Answer Suppose you electrolyze water and obtain 40 cm 3 of hydrogen and 20 cm 3 of oxygen. Then you mix these gases with an additional 10 cm 3 of hydrogen and pass a spark through the mixture. What happens?

Answer for 25 Points Water will be formed ; and 10cm 3 of hydrogen will be left over Back to Board

Show Answer Suppose you pick up a rock in a park. Which element is the rock most likely to contain?

Answer for 25 Points Oxygen Back to Board

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