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professor190 [17]
2 years ago
3

Overtime, crusty scales form on the heating coils inside a kettle. These can be removed by covering the coils with vinegar. As t

he scales disappear, bubbles of gas are observed. Does this method of cleaning a kettle represent a physical or chemical change. Please explain.
Chemistry
1 answer:
Vlad [161]2 years ago
8 0
<span>Chemical change. Crusty scales in this context are limescale. Limescale are found in kettles, hot-water boilers and central heating systems. They are deposited by water on the inside of pipes, kettles, etc. When limescale is introduced to vinegar, the acid in the vinegar helps break down the limescale build-up which creates a chemical reaction. Bubbles will begin rising off and a little heat will be produced. This is because calcium or magnesium carbonate is a base and vinegar is diluted acetic acid ( a weak acid). There's always a chemical reaction between an acid and a base. Heat is always produced between an acid and a base which is a part of what a chemical reaction entails.</span>
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Convert 2.0 M of Phenobarbital sodium (MW: 254 g/mole) solution in water into % w/v and ratio strengths.
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Phenobarbital sodium is a medication that could treat insomnia, for example.

2,0 M of Phenobarbital sodium means 2 moles in 1L.

The concentration units in this case are %w/v that means 1g in 100 mL and ratio strengths that means  1g in <em>r</em> mL. Thus, 2 moles must be converted in grams with molar weight -254 g/mole- and liters to mililiters -1 L are 1000mL-. So:

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