All categories

3 years ago

Which type of changes are melting, freezing, and boiling?

Chemistry

2 answers:

sukhopar [10]3 years ago

8 0

Answer:

the changes are physical changes

tatiyna3 years ago

4 0

Answer:

Adding heat.

Decreasing and increasing temperatures.

Explanation:

You might be interested in

Relationship between light and the color observed?

qaws [65]

Answer:

the color we observe is the wavelength that the object reflects back to us.

Explanation:

light is composed of several wavelengths each wavelengths is a particular color . but for higher wavelengths light becomes invisible. the color we observe is the wavelength of light that the object reflects back to us.

6 0

4 years ago

Chemistry! Help! Please!

Ratling [72]

Question 1

The correct answer is a.

Explanation

The relationship between $pH$ and $pOH$ is given by

$pH + pOH = 14$ , We can use $pH=-log[H^+]$ and $pOH= -log[OH^-]$ . In a we are given the concentration of [OH] and so we use that to find the pOH, then from pOH we can find the pH.

$pOH= -log [2.4 \times 10^-^2] = 1.62\\\\pH = 14 - 1.62= 12.38$

$b.pH=-log(1.53 \times 10^-^2) = 1.82$

c. HCl is a strong acid so it dissociates to 0.0001 $H^+$ and 0.0001 $Cl^-$ , hence

$pH= -log[0.0001] = 4$

$d.pOH= -log [4.4 \times 10^-9] = 8.36\\\\pH= 14- 8.36 = 5.64$

$a.[OH^-] = 2.4 \times 10^-^2$ has a pH 12.36 which is greater than 7

Question 2

The correct answer is d $O_2(g)$ .

Explanation

This is because solids and liquids do not appear in the equilibrium constant expression. Since $K= \frac{[products]}{[reactants]}$ .

For the equation

$2PbS_(_s_) + 3O_2_(_g_) + C_(_s_) \implies 2Pb _(_s_) + CO_2_(_g_) + SO_2(_g_)$

$K= \frac{[CO_2][SO_2]}{[O_2]}$

Question 3

The correct answer is c

In a molecule the oxidation number are assigned to get the sum of a neutral charge or ion. The overall charge of $SO_4^2^-$ is -2 and in all its compounds oxygen has -2 charge, hence

$S+ 4O = -2\\S+4(-2)=-2\\\implies S= -2 +8 = +6$

Question 4

The correct answer is b. An oxidising agent must gain electrons in a reaction, thus it is the one that undergoes reduction.In order find out what is being reduced we write half reactions for molecules that change their state. $Ag^+$ and $K^+$ are spectactor ions in this reaction.

$Cl_2 + 2e \implies 2Cl^-\\\\NO_2 +H_2O \implies NO_3 +2H^+ +2e\\\\H^+ + OH^- \implies H_2O\\$

In the chloride half reaction $Cl_2$ gains electrons to become $Cl^-$ ions.

Question 5

The last element D is correct. When a nucleus decays by beta emission it produces a daughter nucleus that has same mass number but different atomic number. Therefore beta-decay will have equation

$\frac{187}{75} Re \implies \frac{187}{76} Os + \beta$

Question 6

The correct answer is a. A beta particle is an electron because it has a charge of -1 and has same mass as an electron, while a positron is a particle with the same mass as an electron but with a positive charge.

4 0

4 years ago

0.055 grams of PbSO4 is dissolved in 200.00 grams of H2O.

Greeley [361]

Answer:

Solution's mass = 200.055 g

[PbSO₄] = 275 ppm

Explanation:

Solute mass = 0.055 g of lead(II) sulfate

Solvent mass = 200 g of water

Solution mass = Solvent mass + Solution mass

0.055 g + 200 g = 200.055 g

ppm = μg of solute / g of solution

We convert the mass of solute from g to μg

0.055 g . 1×10⁶ μg/ 1g = 5.5×10⁴μg

5.5×10⁴μg / 200.055 g = 275 ppm

ppm can also be determined as mg of solute / kg of solution

It is important that the relation is 1×10⁻⁶

Let's verify: 0.055 g = 55 mg

200.055 g = 0.200055 kg

55 mg / 0.200055 kg = 275 ppm

6 0

3 years ago

Is potassium smaller or larger than a sodium ion

Darina [25.2K]

Sodium ion is smaller than potassium.

8 0

3 years ago

Phenolphthalein has a pKa of 9.7 and is colorless in its acid form and pink in its basic form. calculate [In-}/{HIn} for the fol

zvonat [6]

Answer:

1.58x10⁻⁵

2.51x10⁻⁸

0.0126

63.10

Explanation:

Phenolphthalein acts like a weak acid, so in aqueous solution, it has an acid form HIn, and the conjugate base In-, and the pH of it can be calculated by the Handerson-Halsebach equation:

pH = pKa + log[In-]/[HIn]

pKa = -logKa, and Ka is the equilibrium constant of the dissociation of the acid. [X] is the concentrantion of X. Thus,

i) pH = 4.9

4.9 = 9.7 + log[In-]/[HIn]

log[In-]/[HIn] = - 4.8

[In-]/[HIn] = $10^{-4.8}$

[In-]/[HIn] = 1.58x10⁻⁵

ii) pH = 2.1

2.1 = 9.7 + log[In-]/[HIn]

log[In-]/[HIn] = -7.6

[In-]/[HIn] = $10^{-7.6}$

[In-]/[HIn] = 2.51x10⁻⁸

iii) pH = 7.8

7.8 = 9.7 + log[In-]/[HIn]

log[In-]/[HIn] = -1.9

[In-]/[HIn] = $10^{-1.9}$

[In-]/[HIn] = 0.0126

iv) pH = 11.5

11.5 = 9.7 + log[In-]/[HIn]

log[In-]/[HIn] = 1.8

[In-]/[HIn] = $10^{1.8}$

[In-]/[HIn] = 63.10

6 0

4 years ago

Which type of changes are melting, freezing, and boiling?​

Which type of changes are melting, freezing, and boiling?