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2 years ago

Which of these are physical changes in matter chech all that apply

Chemistry

2 answers:

Bogdan [553]2 years ago

8 0

Explanation:

Changes that are unable to bring any difference in chemical composition of a substance are known as physical change.

For example, change in shape, size, mass, volume, density, boiling or freezing point etc are all physical changes.

Whereas changes that bring difference in chemical composition of a substance are known as chemical changes.

For example, reactivity, toxicity, combustion etc are all chemical changes.

Hence, out of the given options physical changes are classified as follows.

Boiling water

A pencil being sharpened

Freezing water

serious [3.7K]2 years ago

6 0

Answer:

a pencil being sharpened

freezing water

boiling water

Explanation:

a physical change doesn't change the chemical structure of an object. That is why the other 2 are wrong

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How many moles are in 155 grams of aluminum

Aliun [14]

Answer:

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Explanation:

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3 years ago

If 4520 kj of heat is needed to boil a sample of water, what is the mass of water

Cerrena [4.2K]

Answer:

1,085g of water

Explanation:

If we have the value 4520kj is because the question is related to Energy and heat capacity. In this case, the law and equation that we use is the following:

Q= m*C*Δt where;

Q in the heat, in this case: 4520kj

m is the mas

Δt= is the difference between final-initial temperature (change of temperature), in this exercise we don´t have temperatura change.

In order to determine the mass, I will have the same equation but finding m

m= Q/C*Δt without m=Q/C

So: m= 4,520J/4.18J/g°C

m= 1,0813 g

5 0

3 years ago

Nitrogen dioxide and water react to form nitric acid and nitrogen monoxide, like this:

posledela

Answer: The value of the equilibrium constant Kc for this reaction is 3.72

Explanation:

Equilibrium concentration of $HNO_3$ = $\frac{15.5g}{63g/mol\times 9.5L}=0.026M$

Equilibrium concentration of $NO$ = $\frac{16.6g}{30g/mol\times 9.5L}=0.058M$

Equilibrium concentration of $NO_2$ = $\frac{22.5g}{46g/mol\times 9.5L}=0.051M$

Equilibrium concentration of $H_2O$ = $\frac{189.0g}{18g/mol\times 9.5L}=1.10M$

Equilibrium constant is defined as the ratio of concentration of products to the concentration of reactants each raised to the power their stoichiometric ratios. It is expressed as $K_c$