3 (1.5) Rate of reaction change with temp

Question 1

Different ways to measure rates of reactions

Answer 1

-timing how long precipitate takes to form
-measuring decrease in mass
-measuring the volume of gas given off

Question 2

Disappearing cross?

Answer 2

Change in rate of sodium thiosulfate with HCl as temp is changed

Question 3

How does disappearing cross work?

Answer 3

-sodium thiosulfate + HCl are clear, colourless solutions
-react together to form yellow precipitate of sulfur
-can use the amount of time takes for ppt to form as measure of rate of reaction

Question 4

Equation of reaction

Answer 4

Na2​S​ 2​O​ 3​​+2HCl→2NaCl+SO2​​+S+H2​O​

Question 5

Describe method?

Answer 5

-Measure out fixed volumes of sodium thiosulfate and hydrochloric acid using measuring cylinders
-use water bath to gently heat both solutions to desired temperature before you mix them
-Mix solutions in a conical flask place flask over black cross which can be seen through solution
-Record how long it takes for black cross to disappear through cloudy sulfur

Question 6

Issues with method?

Answer 6

-disappeared cross is judged by eye- can be unreliable
-may be delayed reaction time with stopwatch
-low temperature- reaction may be too slow
-may not be enough precipitate for cross to dissapear

Question 7

In an experiment investigating the effect of temperature on rate of reactions what variables will you control

Answer 7

-Concentrations of reactants and products
-Volumes of reactants and products
-Same beaker and cross underneath
-Same person to decide when cross has disappeared