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3 years ago

A chemical change occurs when

Chemistry

1 answer:

trasher [3.6K]3 years ago

6 0

Answer:

Chemical changes occur when bonds are broken and/or formed between molecules or atoms. This means that one substance with a certain set of properties (such as melting point, color, taste, etc) is turned into a different substance with different properties

Explanation:

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(a) Calculate the density of a 374.5-g sample of copper if it has a volume of 41.8 cm3. (b) A student needs 15.0 g of ethanol fo

o-na [289]

Answer:

For a: The density of the sample of copper is $8.96g/cm^3$

For b: The volume of ethanol needed is 19.0 mL

For c: The mass of mercury is 340. grams

Explanation:

To calculate density of a substance, we use the equation:

$\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}$ ......(1)

For a:

Mass of copper = 374.5 g

Volume of copper = $41.8cm^3$

Putting values in equation 1, we get:

$\text{Density of copper}=\frac{374.5g}{41.8cm^3}\\\\\text{Density of copper}=8.96g/cm^3$

Hence, the density of the sample of copper is $8.96g/cm^3$

For b:

Mass of ethanol = 15.0 g

Density of ethanol = 0.789 g/mL

Putting values in equation 1, we get:

$0.789g/mL=\frac{15.0g}{\text{Volume of ethanol}}\\\\\text{Volume of ethanol}=\frac{15.0g}{0.789g/mL}=19.0mL$

Hence, the volume of ethanol needed is 19.0 mL

For c:

Volume of mercury = 25.0 mL

Density of mercury = 13.6 g/mL

Putting values in equation 1, we get:

$13.6g/mL=\frac{\text{Mass of mercury}}{25.0mL}\\\\\text{Mass of mercury}=(13.6g/mL\times 25.0mL)=340.g$

Hence, the mass of mercury is 340. grams

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3 years ago

Paper towel absorbs water is a physical or chemical change?

Marina CMI [18]

It depends. many of the websites i see answering the questions are all over the place, but good luck.

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3 years ago

#1: What is the charge on an electrically neutral atom of hydrogen?

MakcuM [25]

my answer is B.The electrical charge of the hydrogen atom is thought to be exactly zero. This is a consequence of the apparent equality of the magnitude of the electrical charges of the electron and the proton, and their opposite sign. The electrical charge of neutral atoms has been measured to be zero, with an uncertainty of something like 10^(-20) e, where e is the elementary charge.

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4 years ago

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What is endothermic process?

LiRa [457]

Answer:

An endothermic process is any process with an increase in the enthalpy H (or internal energy U) of the system. In such a process, a closed system usually absorbs thermal energy from its surroundings, which is heat transfer into the system. It may be a chemical process, such as dissolving ammonium nitrate in water, or a physical process, such as the melting of ice cubes.

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True or false Products are substances existing before a reaction (usually on left of arrow).

AlladinOne [14]

Answer:

False

Explanation:

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