3 ways to use electric current

5) Calculate the molality of 0.210 mol of KBr dissolved in 0.075kg pure water?

Margaret [11]

Answer:

$\boxed {\boxed {\sf 2.8 \ m }}$

Explanation:

The formula for molality is:

$m=\frac{moles \ of \ solute}{kg \ of \ solvent}$

There are 0.210 moles of KBr and 0.075 kilograms of pure water.

$moles= 0.210 \ mol \\kilograms = 0.075 \ kg$

Substitute the values into the formula.

$m= \frac{ 0.210 \ mol }{0.075 \ kg}$

Divide.

$m= 2.8 \ mol/kg= 2.8 \ m$

The molality is 2.8 moles per kilogram

5 0

3 years ago

Does data from mass spectrometry indicate that modern scientists have made modifications to Dalton''s model? Justify.

Gelneren [198K]

John Dalton was a scientist who proposed that all matter consists of atoms. At this stage, no one had yet discovered neutrons and the nucleus. As a result, Dalton's model consisted of a single atom i.e. the atom was the smallest object.
A mass spectrometer is an instrument that is able to see what is inside an atom. Scientists have been able to prove that the item is not the smallest object in the world. Atoms are made up of smaller objects called protons, neutrons and electrons.
We can, therefore, safely conclude that data from mass spectrometry has helped modern scientists to make modifications to Dalton's model.

5 0

3 years ago

What mass of naoh (40.0 g/mol) is needed to prepare 250 ml of 2 m naoh solution?

laila [671]

20 grams is probably the mass

6 0

3 years ago

An unknown compound displays singlets at δ 2.1 ppm and 2.56 ppm in the ratio of 3:2. what is the structure of the compound?

olasank [31]

1) As can be seen from any 1H NMR chemical shift ppm tables, hydrogens which have δ values from 2ppm to 2.3ppm are hydrogens from carbon which is bonded to a carbonyl group. From this, we can conclude that our hydrogens belong to the type, but from 2 different alkyl groups because of 2 different signals.

2) So, one alkyl group is CH3 and second one can be CH or CH2.

3) If we know that ratio between two types of hydrogens is 3:2, it can be concluded that second alkyl group is CH2.

4) Finally, we don't have any other signals and it indicates that part of the compound which continues on CH2 is exactly the same as the first part.

The ratio remains the same, 3:2 ie 6:4

7 0

3 years ago

Select all that apply. According to scientists, the distribution of volcanoes throughout the world… Is fairly even and widesprea

Ipatiy [6.2K]

Only answers C and D would make sense in this question. Hope I helped please give brainiest!

7 0

3 years ago

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