chem

Question 1

Why use oil instead of water in bath in distillation

Answer 1

some liquids have higher boiling point than water so it needs oil to then evaporate and condense

Question 2

Why do we use white tile in titration under flask

Answer 2

easier to see color change

Question 3

Why cant we use universal indicator in titration

Answer 3

too many ranges of color change

Question 4

How do you know crystallization point

Answer 4

when you stir and see crystals then allow it to cool

Question 5

Why you shouldn’t overheat the crystals in crystallization

Answer 5

you will get dry powder instead of hydrated crystals

Question 6

Why cooling solubility

Answer 6

solubility will decrease so more crystals form to dry them

Question 7

Why do we wash the residue with distilled water in precipitation

Answer 7

remove impurities if its soluble then they wash it to collect all residue left

Question 8

Rate of reaction Why does mass decrease by time

Answer 8

escaping co2

Question 9

Function of cotton wool

Answer 9

prevent the losing of acid, allows escaping of co2

Question 10

Using powdered instead of lumps

Answer 10

higher surface area increasing rate of reaction

Question 11

Measuring temperature

Answer 11

use polystyrene cup instead of beaker

Question 12

Measuring volume

Answer 12

use pipette instead of cylinder

Question 13

How to get more reliable results

Answer 13

repeat experiment and take average

Question 14

Experiment

Answer 14

Write all steps and tools you used in the experiment
Write all the constant variables you used
How you will measure the result
General conclusion
Calculations if any
Equation if any

Question 15

Find % of mass in zinc in brass

Answer 15

Use a balance to find mass of brass
ADD EXCESS SULFURIC ACID Zn + h2so4 makes znso4 + h2
Heat it
Filter to leave behind cu
Wash and Dry
Find mass of cu using a balance
Mass of cu/original mass
Find % of zinc by 100-answer

Question 16

Whats used to grind seashell to form power

Answer 16

crucible

Question 17

how to mash something

Answer 17

pestle and morter

Question 18

Chromatography method

Answer 18

Create the sample using pestle and morter
Dissolve sample in water e.g. water
Calculate rf value
Distance travelled by dye/distance travelled by solvent

Question 19

Collecting gases co2

Answer 19

Limestone - caco3
Put in conical flask with bong put gas syringe on bong
Collects volume of co2
Repeat record calculate average and compare

Question 20

Measuring gas change with mass

Answer 20

Use balance to measure mass in conical flask

cotton wool on top as it stops acid leaving and allows co2 to leave stopping mass decrease too much

Use marble chips and dilute hcl
Measure initial and subtract from final

Question 21

Safety precautions

Answer 21

Cl2 and Hcl makes toxic fumes
Use Fume cupboard