1) How many Joules of energy are released when 75g of water is heated

Is brass a heterogeneous or homogeneous mixture ??????

Lynna [10]

Answer:

Brass is a homogenous mixture of copper and zinc

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4 0

2 years ago

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According to an informal 1992 survey, the drinking water in about one-third of the homes in Chicago had lead levels of about 10

wel

Answer:

10.2 mg

Explanation:

Step 1: Calculate the total amount of water she drank

1 year has 365 days and she lived in Chicago for 2 years = 2 × 365 days = 730 days.

If she drank 1.4 L of water per day, the total amount of water she drank is:

730 day × 1.4 L/day = 1022 L

Step 2: Calculate the amount of Pb in 1022 L of water

The concentration of Pb is 10 ppb (10 μg/L).

1022 L × 10 μg/L = 10220 μg

Step 3: Convert 10220 μg to milligrams

We will use the conversion factor 1 mg = 1000 μg.

10220 μg × 1 mg/1000 μg = 10.2 mg

8 0

2 years ago

What was important about the Hydrogen bright line emission spectrum?

Art [367]

Answer:

The emission spectrum lines are the changes in the quantum energy levels of the single electron in the Hydrogen atom.

Explanation:

Electrons move around the hydrogen atom in electron waves patterns. These waves occur in distinct quantum energy levels.

The change from one quantum energy level to another energy level has a definite energy level change. There is a wave length associated with each change in energy levels. These wave lengths have a color associated with them.

Low energy level changes have long wave lengths associated with them giving red and orange colors.

High energy level changes have short wave lengths associated with them giving blue and violet colors.

Note each atom has a unique emission spectrum associated with the energy levels and electron structure of the atom. Helium was first discovered by looking at its emission spectrum as seen in the sun.

Explanation:

5 0

2 years ago

Reynolds number, for an aorta of 0.9-centimeter diameter, calculate the blood flow in liters per minute when the flow regime in

olga55 [171]

Answer:

Flow in liters per minute is 4 L/min

Explanation:

For this case, we have an aorta of 0.9 cm of diameter (D). Let's suppose an uniform and constant diameter for calculation purposes.

D = (0.9 cm)(1m/100cm)

D = 0.009 m

It is required to calculate the blood flow in liters per minute when the flow regime changes from laminar to turbulent. Laminar flow is usually less than 2500 for Reynolds value, and Turbulent flow when Re is higher than 2500. So, we need to study the phenomenon for

Re = 2500.

Using the definition of Reynolds we can find the velocity average of the blood, and use it to find flow. Where blood density is $\rho$ , aorta diameter is D, average velocity is v and blood viscosity is $\mu$

$Re = \frac{\rho v D}{\mu } \\v = \frac{Re*\mu}{\rho D}$

From data problem, we have Re, D values. As we need blood density and blood viscosity we can find them in medical studies. For example: in this online document: Blood flow analysis of the aortic arch using computational fluid dynamics †

Satoshi Numata, Keiichi Itatani, Keiichi Kanda, Kiyoshi Doi, Sachiko Yamazaki, Kazuki Morimoto, Kaichiro Manabe, Koki Ikemoto, Hitoshi Yaku Author Notes

European Journal of Cardio-Thoracic Surgery, Volume 49, Issue 6, June 2016, Pages 1578–1585, https://doi.org/10.1093/ejcts/ezv459

Published: 20 January 2016

$\rho = 1060 kg/m^3\\\mu = 0.0004 kg/(ms)\\$

$v = \frac{Re*\mu}{\rho D}\\v = \frac{2500 * 0.004 kg/(ms)}{(1060 kg/m3)(0.009 m)}\\v = 1.04 m/s\\$

Average blood velocity is 1.04 m/s. After that, we can calculate the flow (Q) using the flow are (Ao) of aorta.

Q = v*Ao

$Q = (1.4m/s)*(\pi*(0.009m/2)^2)\\Q = 6.67 * 10^-5 \frac{m^3}{s}\\Q = (6.67 * 10^-5 \frac{m^3}{s})(\frac{1000 L}{1 m^3} ) (\frac{60 s}{1 min} )\\Q = 4 L/min$

Finally, the blood flow in liters per minute is 4 L/min when the flow regime in the aorta changes from laminar to turbulent.

7 0

3 years ago

Why is the chemical formula Li2H incorrect? Select the correct answer below: A. There should be one lithium, not two. B. There s

gogolik [260]

Answer:

There should be one lithium, not two.

Explanation:

Lithium reacts with hydrogen at about 750°C to yield lithium hydride (LiH). LiH is white and powdery in appearance. It releases hydrogen gas when it reacts with water.

The correct formula for Lithium hydride is LiH and not Li2H because both lithium and hydrogen are univalent. Lithium has a valency of +1 while hydrogen has a valency of -1 in lithium hydride. Hydrides are formed between hydrogen and highly electro positive metals. In hydrides, hydrogen is forced to accept an electron from the highly electro positive metal.

3 0

3 years ago