In an experiment, hydrochloric acid reacted with different volumes of sodium
thiosulfate in water. A yellow precipitate was formed during the reaction. A cross
drawn at the base of each flask became gradually invisible due the formation of this
yellow precipitate. The time taken for the cross to become invisible was recorded. A
partial record of the experiment is shown.
Experimental Record
Flask Volume of Volume of
Volume of
HCI Sodium Thiosulfate Water
1 10 mL 10 mL
40 mL
2 10 mL 20 ml
10 ml 30 ml
20 mL
4 10 mL 40 mL
10 mL
14 seconds
30 mL
Based on your knowledge of factors that affect the rates of chemical reactions,
predict the trend in the last column of the experimental record. Use complete
sentences to explain the trend you predicted. You do not have to determine exact
values for time; just describe the trend you would expect (increase or decrease) and
why it occurs. (5 points)