What are precautions to be taken when doing titrations? A-Make sure to always vigorously shake that flask after every drop if the end point is still unknown. It may be that the remaining volume of the titrant needed to reach the end point is just adhering on the wall. This is to ensure accuracy. B-The amounts of solid and liquid should be weighed and pipetted with high accurac This is because all the data that will be produced will mainly depend on this. C- If the end point is unknown, dropwise addition of the titrant is recommended. D- Always make sure that the indicator is added. E- All of the above

E

Explanation:

This is because all steps from A-D are important to obtain an accurate result

8

explanation:

each principal energy level above the first contains one s orbital and three p orbitals. a set of three p orbitals, called the p sublevel, can hold a maximum of six electrons. therefore, the second level can contain a maximum of eight electrons - that is, two in the s orbital and 6 in the three p orbitals.

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answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e