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3 years ago

Mr. martin's spanish class is 45 minutes long. if it starts at 3:30, what time does it end?

1 answer:

6 0

Anwser: 4:15

You add 45 minutes to 30 minutes which comes out to be 75 minutes, subtract that from 60 because there are only 60 minutes in an hour, which is 15.. so it's 4:15

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If a pharmacist adds 10 ml of purified water to 30 ml of a solution having a specific gravity of 1.30, calculate the specific gr

xxMikexx [17]

The specific gravity of a sample is the ratio of the density of the sample with respect to one standard sample. The standard sample used in specific gravity calculation is water whose density is 1 g/mL. The solution having specific gravity 1.30 is the density of the sample that is 1.30 g/mL. Thus the weight of the 30 mL sample is (30×1.30) = 39 g.

Now the mass of the 10 mL of water is 10 g as density of water is 10 g/mL. Thus after addition the total mass of the solution is (39 + 10) = 49g and the volume is (30 + 10) = 40 mL. Thus the density of the mixture will be $\frac{49}{40}=1.225$ g/mL. Thus the specific gravity of the mixed sample will be 1.225 g/mL.

6 0

3 years ago

What is the kinetic energy of the emitted electrons when cesium is exposed to UV rays of frequency 1.0×1015Hz?

RideAnS [48]

The kinetic energy of the emitted electrons of cesium when it is exposed to UV rays of frequency $1.0 \times {10^{15}}\;{\text{Hz}}$ is $\boxed{6.63 \times {{10}^{ - 19}}\;{\text{J}}}$

Further Explanation:

Photoelectric effect:

When light is made to fall on any substance, electrons are emitted from it. This is known as the photoelectric effect and the emitted electrons are called photoelectrons. The electrons are emitted because of the transference of energy from light to the electrons.

Cesium is a member of the alkali metal group so it is highly reactive and shows photoelectric effect to the maximum extent. It can remove its electron so easily because of its atomic size. Due to large atomic size of cesium, its outermost electrons are held very less tightly to the nucleus and therefore removed easily.

According to the Planck-Einstein equation, the energy is proportional to the frequency and is expressed as follows:

${\mathbf{E=h\nu }}$ ......(1)

Here,

${\text{E}}$ is the energy.

$h$ is the Plank’s constant.

$\nu$ is the frequency.

The frequency of UV rays is $1.0 \times {10^{15}}\;{\text{Hz}}$ or $1.0 \times {10^{15}}\;{{\text{s}}^{ - 1}}$

The value of Planck’s constant is $6.626 \times {10^{ - 34}}\;{\text{J}}\cdot{\text{s}}$ .

Substitute these values in equation (1)

$\begin{aligned}{\text{E}}&=\left( {6.626 \times {{10}^{ - 34}}\;{\text{J}}\cdot{\text{s}}}\right)\left( {1.0 \times {{10}^{15}}\;{{\text{s}}^{ - 1}}}\right)\\&=6.63\times {10^{ - 19}}\;{\text{J}}\\\end{aligned}$

But when electrons are ejected out from the surface of the substance, all of its energy is considered as kinetic energy.

So the kinetic energy of the electrons is ${\mathbf{6}}{\mathbf{.63 \times 1}}{{\mathbf{0}}^{{\mathbf{ - 19}}}}\;{\mathbf{J}}$ .

Learn more:

1. Statement about subatomic particle: brainly.com/question/3176193

2. The energy of a photon in light: brainly.com/question/7590814

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Structure of the atom

Keywords: kinetic energy, frequency, energy, photoelectric effect, Planck's constant, light, electrons, photoelectrons, proportional, transference, reactive, cesium.

7 0

3 years ago

Read 2 more answers

What is the mass of substance that exactly fills a 247.2 mL container? The density of the substance is 0.81 g/mL. Give the answe

matrenka [14]

Answer:

Explanation:

The density of a substance can be found by using the formula

$Density = \frac{mass}{volume}$

Since we are finding the mass

<h3>mass = Density × volume</h3>

From the question

Density = 0.81 g/mL

volume = 247.2 mL

Substitute the values into the above formula and solve for the mass

mass = 0.81 × 247.2

= 200.232

We have the final answer as

<h3>mass = 200.23 g to 2 decimal places</h3>

Hope this helps you

3 0

3 years ago

Which example indicates that a chemical change has occurred? *

andrezito [222]

Answer:

A. When two aqueous solutions are mixed, a precipitate is formed.

Explanation:

The precipitate (a solid substance that falls from the liquid) is the result of a chemical reaction taking place between the liquids.

The other three answer choices are indicative of physical changes (temperature change, phase change, color change).

7 0

3 years ago

Maple syrup, which comes from the sap of maple trees, contains water and natural sugars. It's a clear, brown liquid and the suga

il63 [147K]

Maple syrup would be categorized under solutions. As it contains sugar which is very soluble in water, it dissolves completely in water depending on its solubility at that temperature making it impossible for the components to be filtered out. A solution is a homogeneous mixture.

6 0

3 years ago