Pre-Test Key Name: Chemical Reactions Date: 1. The chart below shows the amount of gas that is produced when two reactants (a solid and a liquid) are combined. However, one of the boxes is missing information. Which is most likely the missing value? A. 29 B. 172 C. 246 D. 413 Reactant A (g) Reactant B Product 2 20 250 3.3 33 1 10 150 2. When zinc (Zn) is added to hydrochloric acid (HCl), hydrogen gas (H 2 ) is produced. The graph below shows the volume of hydrogen gas produced when different quantities of hydrochloric acid are added to 5g of zinc. Explain why the graph s line flattens out at a certain point. 1200 1000 Volume H2 gas 800 600 400 200 0 0 20 40 60 80 100 120 Volume of HCl Student answers may vary. In order for a reaction to take place, both products must be present in the reaction. Once one reactant is used up, the reaction can no longer take place. The flat line on the graph indicates that 50 ml of hydrochloric acid causes all of the zinc to completely react. Adding more hydrochloric acid will not increase the volume of gas produced because there won t be enough zinc to react to the extra acid 1
3. Peter is timing the rate of reaction between two substances when they are combined. The amount of each reactant that will be used for each trial is shown in the table below. Which trial will likely have the fastest rate of reaction? Trial Reactant A Reactant B 1 2g 10ml 2 2g 20ml 3 2g 30ml A. Trial 1 B. Trial 2 C. Trial 3 D. The reaction rate will be the same for all Trials. 4. True or False An increase in temperature is an indication that a chemical reaction is occurring between two reactants. 5. Which of the following is most likely NOT a chemical reaction? A. NaCl + H 2 O H 2 O + NaCl B. Two substances combine and produce hydrogen gas. C. Two reactants combine to form two products. D. All of the above. 2
6. Considering the types and numbers of reactants and products, which of the following is a valid equation for a chemical reaction? A. Na + Cl NaCl + 2H 2 O Sodium Chlorine Sodium Chloride Water B. 2Ag + S Ag 2 S Silver Sulfur Silver Sulfide C. H 2 + S H 2 O Hydrogen Sulfur Water D. All of the above 7. Adam combined vinegar and baking soda inside the flask and balloon below. During the reaction, the baking soda was used up. Also, gas was created and trapped inside the balloon. Before the reaction, the flask and the reactants had a mass of 300 g. What statement could be made about the total mass of the flask s contents after the reaction? A. The mass is greater than 300g. B. The mass is less than 300 g. C. The mass equals 300g. D. The mass cannot be determined. 3
8. True or False The amount of product that can be produced is determined by the rate of reaction. 9. Four students are combining reactants to produce chemical reactions. The amount of each reactant and the catalyst that the students used are shown in the table below. All four reactions are presented in the table below. Based on the information in the table, which reaction graphed probably shows Mary s results. Student Name Reactant A (g) Reactant B Catalyst Bill 10 10 2 Mary 100 0 100 Jen 50 50 10 Sam 20 50 10 A. Reaction 1 B. Reaction 2 C. Reaction 3 D. Reaction 4 10. Keith is combining two reactants in order to create a chemical reaction. If he adds a catalyst to the reactants as well, what can he expect to happen? A. The rate of reaction will change. B. The amount of product will increase. C. The amount of product will decrease. D. The catalyst will have no effect on the reaction. 4
11. Look at the chemical reaction below. Which of the following is a product of the reaction? CH 4 + 2O 2 CO 2 + 2H 2 O + Heat Methane Gas Oxygen Carbon Dioxide Water A. Heat B. CH 4 C. CO 2 D. A and C 12. True or False Sometimes a product can look unchanged even though a chemical reaction has taken place. 13. Ben, Dave and Mary are each combining two solutions: hydrochloric acid (HCl) and sodium hydroxide (NaOH). The equation for this chemical reaction is shown below. The chart shows the volumes and concentrations that the students used when preparing their reactions. Should each student get the same amount of product when the reactions are complete? Explain your answer. HCl + NaOH NaCl + H 2 O Hydrochloric Acid Sodium Hydroxide Sodium Chloride Water Student Concentration of HCl and NaOH (g/100 ml) Volume of HCl and NaOH Ben 5.4 30 Dave 10.8 30 Mary 16.2 30 Student answers may vary. The amount of reactants increases when their concentrations increase but their volumes stay the same. Therefore, even though each student is using the same volume of reactants, they are using different amounts of reactants because the concentrations are different. Ben s reaction will produce the least amount of product while Mary s reaction will produce the most product. 5