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3 years ago

Is "dissolving in water" a chemical change or a physical change?

Chemistry

2 answers:

Schach [20]3 years ago

8 0

Answer:

In fact this should be considered more of a continuum. For example salt dissolving in water is usually considered to be a physical change, however the chemical species in salt solution (hydrated sodium and chlorine ions) are different from the species in solid salt.

Explanation:

Hope this helps! Brainly me <3

JulijaS [17]3 years ago

3 0

A physical Change

Explanation:

BECAUSE the dissolving material can solidify after a while

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Zn(s) + 2HCl(aq) -> ZnCl2(aq) + H2(g) Which half reaction correctly describes the oxidation that is taking place?

abruzzese [7]

Zn (s) -> Zn+2 (aq) + 2e-

Zn (s) with a neutral charge is oxidized and looses two electrons in the process to form ZnCl2 (aq) where Zn has a charge of 2+.

8 0

3 years ago

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What is the theoretical yield of Li3N in grams when 12.8 g of Li is heated with 34.9 g of N2?

Olenka [21]

Answer:- 21.4 grams of $Li_3N$ are formed.

Solution:- The balanced equation is:

$6Li+N_2\rightarrow 2Li_3N$

From this equation, lithium and nitrogen reacts in 6:1 mol ratio. Limiting reactant gives the theoretical yield of the product. We will calculate the grams of the product for the given grams of both the reactants and see which one of them gives the limited amount of the product. This limited amount of the product will be the theoretical yield.

The molar mass of Li is 6.94 gram per mol and for $N_2$ It is 28.02 gram per mol. The molar mass of $Li_3N$ is 34.83 gram per mol. The calculations for the grams of the product for given grams of both the reactants are shown below:

$12.8gLi(\frac{1molLi}{6.94gLi})(\frac{2molLi_3N}{6molLi})(\frac{34.83gLi_3N}{1molLi_3N})$

= $21.4gLi_3N$

$34.9gN_2(\frac{1molN_2}{28.02gN_2})(\frac{2molLi_3N}{1molN_2})(\frac{34.83gLi_3N}{1molLi_3N})$

= $86.8gLi_3N$

From above calculations, Li gives least amount of the product. So, 21.4 g of $Li_3N$ are formed.

4 0

3 years ago

The whiye pigment TiO2 is prepared by the reaction of titanium tetrachloride, TiCl4, with water vapor in the gas phase:

omeli [17]

Answer:

$\boxed{\text{62.1 kJ}}$

Explanation:

The formula for calculating the enthalpy change of a reaction by using the enthalpies of formation of reactants and products is

$\Delta_{\text{r}}H^{\circ} = \sum \Delta_{\text{f}} H^{\circ} (\text{products}) - \sum\Delta_{\text{f}}H^{\circ} (\text{reactants})$

TiCl₄(g) + 2H₂O(g) ⟶ TiO₂(s) + 4HCl(g)

ΔH°f/kJ·mol⁻¹: -763.2 -241.828 -939.7 -92.307

$\begin{array}{rcl}\Delta_{\text{r}}H^{\circ} & = & [-939.7 + 4(-92.307)] - [-763.2 + 2(-241.828)\\& = & [-939.7 - 369.228] - [-763.2 - 483.656]\\& = & -1308.928 + 1246.856\\& = & \mathbf{-62.1}\\\end{array}\\\text{The amount of heat evolved is } \boxed{\textbf{62.1 kJ}}$

5 0

3 years ago

Which substance can be broken down by chemical means?

zepelin [54]

Methanol is the substance that can be broken down by chemical means, the remaining ones are elements.

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3 years ago

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C. Another radioisotope of americium exists which has an atomic mass of 242.

ollegr [7]

Answer:

1 g

Explanation:

The half-life of Am-242 (16 h) is the time it takes for half of it to disappear.

We can make a table of the mass left after each half-life.

$\begin{array}{cccc}\textbf{No. of} & & \textbf{Percent} & \textbf{Mass}\\\textbf{Half-lives} & \textbf{Time/h} & \textbf{Remaining} & \textbf{Remaining/g}\\0& 0 & 100 & 8\\1 & 16 &50 & 4\\2 & 32 & 25 & 2\\3 & 48 & 12.5 & 1\\4 & 64 & 6.25 & 0.5\\\end{array}$

The mass remaining after 48 h is 1 g.

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3 years ago