Chemistry, 18.10.2019 14:20 whitakers87

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lists of observable changes that suggest a chemical or physical change has occurred?

lists of observable changes that suggest a chemical or physical change has occurred?

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Answer from: kiingbr335yoqzaxs

Physical change is a change in color texture and ect chemical is the change in the actual substance

Answer from: frankierice020

CHEMICAL CHANGES
1. rusting of iron
2. combustion (burning) of wood
3. metabolism of food in the body
4. mixing an acid and a base, such as hydrochloric acid (HCl) and sodium hydroxide (NaOH)
5.cooking an egg
6.digesting sugar with the amylase in saliva
7. mixing baking soda and vinegar to produce carbon dioxide gas
8.baking a cake
9. electroplating a metal
10. using a chemical battery
11. explosion of fireworks
12. rotting bananas
13. grilling a hamburger
14. milk going sour

PHYSICAL CHANGES
1. crushing a can
2. melting an ice cube
3. boiling water
4. mixing sand and water
5. breaking a glass
6. dissolving sugar and water
7. shredding paper
8. chopping wood
9. mixing red and green marbles
10. sublimating dry ice
11. crumpling a paper bag
12. chopping an apple
13. mixing salt and sand

Answer from: Quest

Acovalent bond is formed between the two hydrogen bonds

Answer from: Quest

answer: - first one is the correct answer. $k_2s(aq)+cocl_2(aq)\rightarrow 2kcl(aq)+cos(s)$ .

explanations: - potassium sulfide is $k_2s$ and cobalt(ii) chloride is $cocl_2$ .

charge on k is +1, charge on s is -2, charge on co is +2 and charge on cl is -1.

in a double replacement reaction the ion exchange takes place. in general the reaction looks like:

$ab+cd\rightarrow ad+cb$

if one of the product is insoluble as per solubility rules then a precipitate of it is formed.

when we mix the aqueous solutions of potassium sulfide and cobalt(ii) chloride then chloride ion goes with potassium ion and sulfide ion goes with cobalt ion and the balanced equation is written as:

$k_2s(aq)+cocl_2(aq)\rightarrow 2kcl(aq)+cos(s)$

k and cl has equal charges, similarly co and s has equal charges and hence no subscripts are used for the product side.

as per the solubility rules, cos is insoluble and so it's precipitate is formed.

looking at the given choices, first choice is correct.

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