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3 years ago

Please write down the definitions of elements, compounds, mixtures, homogenous mixtures, and heterogenous mixtures.

2 answers:

7 0

If it is pure, the substance is either an element or a compound. If a substance can be separated into its elements, it is a compound. If a substance is not chemically pure, it is either a heterogeneous mixture or a homogeneous mixture. If its composition is uniform throughout, it is a homogeneous mixture

MA_775_DIABLO [31]3 years ago

3 0

A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture.

A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture.

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A chemistry student needs 45.0mL of pentane for an experiment. By consulting the CRC Handbook of Chemistry and Physics, the stud

Masja [62]

The mass of pentane the student should weigh out is

The density of pentane is 0.626 gcm-3

To calculate the mass of pentane following expression is used,

(Density is defined as the mass divide by volume)

Density = mass / volume

mass of pentane = Density of pentane * Volume of pentane

mass of pentane = 0.626 gcm-3 * 45.0 mL

= 28.17 g

Here the unit of mass of pentane is g,

However the unit of density is gcm-3 and unit of volume is mL i.e. cm3

Hence, Mass = gcm-3 * cm3

Mass = g

The mass of pentane the student should weigh out is 28.17g

Learn more about Density on

brainly.com/question/1354972

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5 0

2 years ago

The closeness of a measurement to its true value is a measure of its _____.

svlad2 [7]

The closeness of a measurement to its true value is a measure of its accuracy. This term is the degree of which a certain measurement conforms to the correct value or the standard value. It is not the same with the term precision. Precision, on the other hand, is a measure used to characterize the closeness of the data measured.

7 0

3 years ago

Read 2 more answers

How many grams of h2 will be produced if 175g of HCI are allowed to react completely with sodium

Sedbober [7]

Answer:

4.8 grams of H₂ will be produced if 175g of HCI are allowed to react completely with sodium

Explanation:

By stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction) you can see that the following amounts in moles of each compound react and are produced:

HCl: 2 moles
Na: 1 mole
NaCl: 2 moles
H₂: 1 mole

You know the following masses of each element:

H: 1 g/mole
Cl: 35.45 g/mole
Na: 23 g/mole

So, the molar mass of each compound participating in the reaction is:

HCl: 1 g/mole + 35.45 g/mole= 36.45 g/mole
Na: 23 g/mole
NaCl: 23 g/mole + 35.45 g/mole= 58.45 g/mole
H₂: 2* 1 g/mole= 2 g/mole

Then, by stoichiometry of the reaction, the following amounts in grams of each of the compounds participating in the reaction react and are produced:

HCl: 2 moles* 36.45 g/mole= 72.9 g
Na: 1 mole* 23 g/mole= 23 g
NaCl: 2 moles* 58.45 g/mole= 116.9 g
H₂: 1 mole* 2 g/mole= 2 g

So, a rule of three applies as follows: if by stoichiometry, when reacting 72.9 grams of HCl 2 grams of H₂ are formed, when reacting 175 grams of HCl how much mass of H₂ will be formed?

$mass of H_{2} =\frac{175 g of HCl*2g ofH_{2} }{72.9 g of HCl}$

mass of H₂= 4.8 g

<u><em>4.8 grams of H₂ will be produced if 175g of HCI are allowed to react completely with sodium</em></u>

3 0

3 years ago

Read 2 more answers

Draw structure of oxygen, nitrogen &methane.

Elina [12.6K]

See the image below-⬇⬇-

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4 0

3 years ago

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What is litmus paper used for? To indicate if all the reactants have been used up to determine if a chemical reaction has occurr

rjkz [21]

The main use of litmus is to test whether a solution is acidic or basic. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F).

8 0

3 years ago