HELP PLS WILL GIVE BRAINLIEST AND THANKS

Water boils at rate of ........and freeze at ........

Schach [20]

100 degree celcius and 0 degree Celsius

7 0

3 years ago

Calculate the number of grams of sodium chloride in the solution. (Hint: Remember that sodium chloride is a strong electrolyte.)

creativ13 [48]

The question is incomplete, here is the complete question:

A solution contains 0.115 mol $H_2O$ and an unknown number of moles of sodium chloride. The vapor pressure of the solution at 30°C is 25.7 torr. The vapor pressure of pure water at this temperature is 31.8 torr. Calculate the number of grams of sodium chloride in the solution. (Hint: Remember that sodium chloride is a strong electrolyte.)

<u>Answer:</u> The mass of sodium chloride in the solution is 0.714 grams

<u>Explanation:</u>

The formula for relative lowering of vapor pressure will be:

$\frac{p^o-p_s}{p^o}=i\times \chi_{\text{solute}}$

where,

$p^o$ = vapor pressure of solvent (water) = 31.8 torr

$p^s$ = vapor pressure of the solution = 25.7 torr

i = Van't Hoff factor = 2

$\chi_{\text{solute}}$ = mole fraction of solute (sodium chloride) = ?

Putting values in above equation, we get:

$\frac{31.8-25.7}{31.8}=2\times \chi_{NaCl}\\\\\chi_{NaCl}=0.0959$

Mole fraction of a substance is calculated by using the equation:

$\chi_A=\frac{n_A}{n_A+n_B}$

$\chi_{\text{NaCl}}=\frac{n_{\text{NaCl}}}{n_{\text{NaCl}}+n_{\text{water}}}$

We are given:

Moles of water = 0.115 moles

$0.0959=\frac{n_{\text{NaCl}}}{n_{\text{NaCl}}+0.115}\\\\n_{\text{NaCl}}=0.0122mol$

To calculate the mass for given number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Moles of NaCl = 0.0122 moles

Molar mass of NaCl = 58.5 g/mol

Putting values in above equation, we get:

$0.0122mol=\frac{\text{Mass of NaCl}}{58.5g/mol}\\\\\text{Mass of NaCl}(0.0122mol\times 58.5g/mol)=0.714g$

Hence, the mass of sodium chloride in the solution is 0.714 grams

5 0

3 years ago

Calculate the mass of 29.8 mL of aluminum, which has a density of 2.00 g/mL.

MaRussiya [10]

Answer:

The answer is

Explanation:

The mass of a substance when given the density and volume can be found by using the formula

<h3>mass = Density × volume</h3>

From the question

Density of aluminum = 2.00 g/mL

volume = 29.8 mL

The mass is

mass = 2 × 29.8

We have the final answer as

Hope this helps you

5 0

2 years ago

What observation about light supported Einstein's theory?

Llana [10]

In 1905 Albert Einstein had proposed a solution to the problem of observations made on the behaviour of light having characteristics of both wave and particle theory. From work of Plank on emission of light from hot bodies, Einstein suggested that light is composed of tiny particles called <span>photons, </span>and each photon has energy.

Light theory branches in to the physics of <span>quantum mechanics, </span>which was conceptualised in the twentieth century. Quantum mechanics deals with behaviour of nature on the atomic scale or smaller.

As a result of quantum mechanics, this gave the proof of the dual nature of light and therefore not a contradiction.

5 0

3 years ago

In your own words, describe two conditions that are necessary for an eclipse to occur

Rzqust [24]

1. the Moon must be in line with the Earth and Sun - New Moon for a solar eclipse and Full Moon for a lunar eclipse.2. the Moon must be at one of its nodes. Most of the time the Moon at New or Full passes above or below the Sun because its orbit is tilted relative to the ecliptic. An eclipse can occur only when it is at a node, in other words crossing the ecliptic.

4 0

3 years ago