F2 SCIENCE!! HELP PLX! 15POINTS!

Angel15

2008-03-21 3:51 am

1.The table below shows five acid-alkali indicators and their colours at different pH values.

IndicatorpH value
P1-2:Red 5-12: Yellow
Q1-6:Yellow 7.5-12:blue
R1-5:Red 8-12:blue
S1-8:colourless 10-12:Red
T1:Red 2-8:Yellow 10-12:Blue

A) Explain how you would use two of the indicators to make sure that a solution has a pH value of about 2.

2. During winter when northeastly wind blows from Guangdong to HK, the pH value of the rainwater in Sheung Shui and Sai kung usually decreases.

A) What does this tell us about the acidity of the rainwater?
B) Why does this happen?

3.Oven cleaners is a household substance that contains caustic soda, what hazard warning label should be placed on the container of this substance?

回答 (1)

Chiu

2008-03-21 5:48 am

✔ 最佳答案

1a)
Since R have a RED colour in acidic solution,first,add indicator R to the sample of solution.Red colour shows the solution is ACIDIC.
P have a RED colour in pH1-pH2 solution,so,add P to another sample of the solution.The red colour shows the soltion has a pH about 2.
2a)
The rainwater is more acidic than normal.
b)
There are factories in Guangdong province,the factories release acidic gas which causes acid rain,and the gas blow to Hong Kong by northeastly wind,so acid rain occur in Hong Kong.Since Sheung Shui and Sai kung is in the northern part of Hong Kong,acidic rainwater is more likely to happen in these places.
3)
Caustic soda is sodium hydroxide,it is a strong alkali which can corrose skin.So,a CORROSIVE label should be placed on the container of this substance.

2008-03-21 13:18:18 補充：
Acidic gas are sulphur dioxide,nitrogen dioxide.

參考: Myself

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