SC18bii Core Practical 1 and 2

Question 1

core practical - gas produced for small marble chips and hydrochloric acid

Answer 1

A~ set up apparatus (conical flask with tube underwater to a measuring cylinder)
B~ measure 40cm2 of dilute HCl into the conical flask
C~ add 5g of small marble chips to the flask
D~ immediately stopper the flask and start the stop clock
E~ note the amount of gas produced from the measuring cylinder
F~ repeat using big marble chips and then different concentrations of HCl

Question 2

word equation for marble and hydrochloric acid

Answer 2

Calcium carbonate + Hydrochloric Acid → Calcium chloride + Carbon dioxide + water​

Question 3

state the dependent and Independent variables for the practical between marble and HCl

Answer 3

dependant - volume of gas produced
Independent - Size/surface area of marble chips and concentration of acid

Question 4

state the control variables for the practical between marble and HCl

Answer 4

~temperature
~volume of acid
~mass of marble chips​

Question 5

core practical - changing rates of reactions (sodium thiosulfate + HCl)

Answer 5

A - place 50cm3 of sodium thiosulfate solution into conical flask
B - measure out 5cm3 of dilute HCl
C - heat conical flask in water bath at a certain temp (note temp down)
D - remove flask when temp is achieved and place it on a piece of paper with a black cross
E - add HCl to flask and start stop clock
F - stop the clock when cross disappear and note down the time
G - repeat with different temps

Question 6

why does the cross disappear?

Answer 6

because the precipitate (solid) settles at the bottom of the flask

Question 7

how can you improve results from any practical?

Answer 7

repeat it with the same conditions and average both of the results