Convert this temperature from F to C 26.6°c 93.600 62.2°C 5.7°C

At constant pressure, which of these systems do work on the surroundings? Check all that apply.

lana66690 [7]

I believe the correct answers from the choices listed above are the second and the last option. At constant pressure, the systems 2A(g) + B(g) ---> 4C(g) and 2C(g) A(s) + B(s) ---> C(g) produces work to the surroundings. When a gas is evolved during a chemical reaction, the gas can be imagined as displacing the atmosphere - pushing it back against the atmospheric pressure. The work done is therefore V*P where V is the volume of gas evolved, and P is the atmospheric pressure.

6 0

3 years ago

Compute the atomic density (the number of atoms per cm3 ... rather than the mass density g/cm3) for a perfect crystal of silicon

serious [3.7K]

Answer:

$\large\boxed{\large\boxed{5.00\times 10^{22}atoms/cm^3}}$

Explanation:

You can convert the density into atomic density using the atomic weight and Avogadro's number

A dimensional analysis is very helpful:

$\dfrac{g}{cm^3}\times \dfrac{mol}{g}\times \dfrac{atoms}{mol}=\dfrac{atoms}{cm^3}$

Follow the chain: g cancels with g, mol cancels with mol; at the end, what remains is atoms/cm³, which is what you want.

Use that with your data:

$\dfrac{2.33g}{cm^3}\times \dfrac{1mol}{28.09g}\times \dfrac{6.022\times 10^{23}atoms}{mol}=\approx 5.00\times10^{22}atoms/cm^3$

3 0

3 years ago

The polyatomic nitrate ion (NO3−) is present in both the products and the reactants of the chemical equation shown below.

Diano4ka-milaya [45]

Answer:

There is one nitrate ion in the products, and two in the reactants of this equation.

Explanation:

1: We know a nitrate ion has the formula $NO_{3}^{-$ , so we just need to count how many of them are on each side of the equation.

2: To find how many are in the reactants of the equation, you look at the left hand side (before the arrow). You can see the section $(NO_{3} )_{2}$ , which shows that there are two nitrate ions in the reactant side (as seen by the little 2).

3: To find how many are on the products side, you do the same thing - this time there is only one $NO_{3}^{-$ in the lithium nitrate.

So, there is one nitrate ion in the products, and two in the reactants of this equation.

7 0

3 years ago

Read 2 more answers

What mass of solid sodium formate (of MW 68.01) must be added to 150 mL of 0.42 mol/L formic acid (HCOOH) to make a buffer solu-

Sergio [31]

Answer:

We need 4.28 grams of sodium formate

Explanation:

Step 1: Data given

MW of sodium formate = 68.01 g/mol

Volume of 0.42 mol/L formic acid = 150 mL = 0.150 L

pH = 3.74

Ka = 0.00018

Step 2: Calculate [base)

3.74 = -log(0.00018) + log [base]/[acid]

0 = log [base]/[acid]

0 = log [base] / 0.42

10^0 = 1 = [base]/0.42 M

[base] = 0.42 M

Step 3: Calculate moles of sodium formate:

Moles sodium formate = molarity * volume

Moles of sodium formate = 0.42 M * 0.150 L = 0.063 moles

Step 4: Calculate mass of sodium formate:

Mass sodium formate = moles sodium formate * Molar mass sodium formate

Mass sodium formate = 0.063 mol * 68.01 g/mol

Mass sodium formate = 4.28 grams

We need 4.28 grams of sodium formate

4 0

3 years ago

How much heat is absorbed by a 112.5 g sample of water when it is heated from 12.5 °C to 92.1 °C? (Specific heat capacity of wat

Alborosie

Answer:

$\boxed {\boxed {\sf37,467.72 \ Joules }}$

Explanation:

We are asked to find how much heat a sample of water absorbed. Since we are given the mass, temperature, and specific heat, we will use the following formula.

$q=mc \Delta T$

The mass (m) of the sample is 112.5 grams. The specific heat capacity of water (c) is 4.184 Joules per gram degree Celsius. The difference in temperature (ΔT) is found by subtracting the initial temperature from the final temperature.