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3 years ago

Lily is doing a science experiment with a substance in a sealed jar. At first,

Chemistry

1 answer:

Serhud [2]3 years ago

6 0

Answer:

Faster, and the substance will be a gas.

Explanation:

I'm quite not sure with it. But, I've tried my best. Since maybe the substance is liquid

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Label each of the following changes as a physical change or chemical change. Give evidence to support your answer.

SVEN [57.7K]

Answer:

A catalytic converter changes nitrogen dioxide to nitrogen gas and oxygen gas is a chemical change.

Explanation:

Hello.

In this case, since physical changes do not modify the molecular composition and structure of the material undergoing it whereas the chemical change does, for catalytic converters we should know they promote chemical reaction in which the composition is changed; for instance, for the given example, the following chemical reaction is the evidence:

$2NO_2\rightarrow N_2+O_2$

As you can see, nitrogen and oxygen are no longer bonded but separated by themselves, therefore, this is a chemical change.

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3 0

2 years ago

A 52.9g sample of brass, which has a specific heat capacity of 0.375Â·JÂ·g^âˆ’1Â°C^âˆ’1, is put into a calorimeter (see sketch a

vaieri [72.5K]

Answer: 90.04°C

Explanation: <u>Calorimeter</u> is a device measures the amount of heat of a chemical or physical process. An ideal calorimeter is one that is well-insulated, i.e., prevent the transfer of heat between the calorimeter and its surroundings. So, the net heat change inside the calorimeter is zero:

$q_{1}+q_{2}=0$

Rearraging, it can be written as

$q_{1}=-q_{2}$

showing that the heat gained by Substance 1 is equal to the energy lost by Substance 2.

In our case, water is gaining heat, because its temperature has risen and so, brass is losing energy:

$q_{water}=-q_{brass}$

Calculating:

$m_{w}.c_{w}.\Delta T=-[m_{b}.c_{b}.\Delta T]$

$100.4.18.(18.4-15)=-[52.9.0.375.(18.4-T)]$

Note: final temperature is the same as the substances are in thermal equilibrium.

Solving:

418(3.4)= - 365.01 + 19.8375T

19.8375T = 1786.21

T = 90.04

The initial temperature for the sample of brass was 90.04°.

7 0

2 years ago

If 0.340 mol of a nonvolatile nonelectrolyte are dissolved in 3.10 mol of water, what is the vapor pressure PH2O of the resultin

SIZIF [17.4K]

Answer:

21.4 torr

Explanation:

The vapour pressure of a solution is lower than that of the pure solvent. And according to Raoult's law this depends of the amount of solute in the solvent. It is calculated according to the following equation

$P_{A} =X_{A} P^{o} _{A}$