Learn Some Basic Concepts of Chemistry with Free Lessons & Tips

To convert a temperature from Fahrenheit (°F) to Celsius (°C), you can use the following formula:

C=5/9×(F−32)

Given that the measured temperature is 200°F, let's substitute this value into the formula:

C=5/9×(200−32)

C=5/9×168

C≈840/9

C≈93.33°

So, the correct answer is:

(c) 93.3°C

Number of moles=Mass/Molar mass

Number of moles=5.85 g/58.44g

Number of moles≈0.1 molNumber of moles≈0.1mol

Next, we need to convert the volume of the solution from milliliters (mL) to liters (L):

V=500 mL/1000 mL
V=0.5 L

Now, we can calculate the molarity:

M=0.1 mol/0.5 L

M=0.2 mol/L

So, the correct answer is:

(c) 0.2 mol L^-1

First, let's calculate the number of moles for each given mass of the elements using the formula:

Number of moles=Given massMolar massNumber of moles=Molar massGiven mass

Then, we can calculate the number of atoms for each element using the formula:

Number of atoms=Number of moles×Avogadro’s numberNumber of atoms=Number of moles×Avogadro’s number

Now, let's perform the calculations for each option:

(a) For 4g He: Number of moles=4 g4.0026 g/mol≈0.9996 molNumber of moles=4.0026g/mol4g≈0.9996mol Number of atoms=0.9996×6.022×1023≈6.027×1023Number of atoms=0.9996×6.022×1023≈6.027×1023

(b) For 46g Na: Number of moles=46 g22.9898 g/mol≈2.0003 molNumber of moles=22.9898g/mol46g≈2.0003mol Number of atoms=2.0003×6.022×1023≈1.2042×1024Number of atoms=2.0003×6.022×1023≈1.2042×1024

(c) For 0.40g Ca: Number of moles=0.40 g40.078 g/mol≈0.009978 molNumber of moles=40.078g/mol0.40g≈0.009978mol Number of atoms=0.009978×6.022×1023≈6.0085×1021Number of atoms=0.009978×6.022×1023≈6.0085×1021

(d) For 12g He: Number of moles=12 g4.0026 g/mol≈2.996 molNumber of moles=4.0026g/mol12g≈2.996mol Number of atoms=2.996×6.022×1023≈1.8026×1024Number of atoms=2.996×6.022×1023≈1.8026×1024

Comparing the calculated number of atoms for each option, we find that:

The greatest number of atoms is present in 12 g He (Option d).

To find the number of molecules of H2SO4H2SO4 present in 100 mL of a 0.02 M H2SO4H2SO4 solution, we need to first calculate the number of moles of H2SO4H2SO4 present in the solution using the given concentration.

Given:

• Concentration of H2SO4H2SO4 solution = 0.02 M
• Volume of H2SO4H2SO4 solution = 100 mL = 0.1 L

Using the formula for molarity, M=molesvolume (in L)M=volume (in L)moles, we can rearrange it to find the number of moles:

moles=M×volume (in L)moles=M×volume (in L)

moles=0.02 mol/L×0.1 Lmoles=0.02mol/L×0.1L

moles=0.002 molmoles=0.002mol

Now, to find the number of molecules, we'll use Avogadro's number, 6.022×10236.022×1023 molecules/mol:

Number of molecules=moles×Avogadro’s numberNumber of molecules=moles×Avogadro’s number

Number of molecules=0.002 mol×6.022×1023 molecules/molNumber of molecules=0.002mol×6.022×1023molecules/mol

Number of molecules=1.2044×1021 moleculesNumber of molecules=1.2044×1021molecules

So, the correct answer is:

(a) 1.2044×10211.2044×1021 molecules

To find the mass percent of carbon in carbon dioxide (CO2CO2), we need to calculate the mass of carbon in one molecule of carbon dioxide and then express it as a percentage of the total mass of carbon dioxide.

The molecular formula of carbon dioxide is CO2CO2. It contains one atom of carbon (C) and two atoms of oxygen (O).

The atomic mass of carbon (C) is approximately 12.01 g/mol, and the atomic mass of oxygen (O) is approximately 16.00 g/mol.

Therefore, the molar mass of CO2CO2 can be calculated as:

Molar mass of CO2=1×Molar mass of C+2×Molar mass of OMolar mass of CO2=1×Molar mass of C+2×Molar mass of O Molar mass of CO2=1×12.01 g/mol+2×16.00 g/molMolar mass of CO2=1×12.01g/mol+2×16.00g/mol Molar mass of CO2=12.01 g/mol+32.00 g/molMolar mass of CO2=12.01g/mol+32.00g/mol Molar mass of CO2=44.01 g/molMolar mass of CO2=44.01g/mol

The mass percent of carbon in CO2CO2 can be calculated using the formula:

Mass percent of carbon=Mass of carbonTotal mass of CO2×100Mass percent of carbon=Total mass of CO2Mass of carbon×100

Mass percent of carbon=12.01 g/mol44.01 g/mol×100Mass percent of carbon=44.01g/mol12.01g/mol×100

Mass percent of carbon≈12.0144.01×100≈27.27%Mass percent of carbon≈44.0112.01×100≈27.27%

So, the correct answer is:

(b) 27.27%

To find the mass of the solution, we can use the formula:

Mass=Volume×DensityMass=Volume×Density

Given:

• Density of the solution = 3.12 g/mL
• Volume of the solution = 1.5 mL

Mass=1.5 mL×3.12 g/mLMass=1.5mL×3.12g/mL

Mass=4.68 gMass=4.68g

To express the mass in proper significant figures, we consider that the volume measurement (1.5 mL) has two significant figures. Therefore, the result should also have two significant figures.

So, the correct answer is:

(c) 4.680 g

At STP (Standard Temperature and Pressure), one mole of any gas occupies a volume of 22.4 liters.

Given that we're dealing with oxygen gas (O2O2), and we know Avogadro's number is 6.022×10236.022×1023 entities per mole, let's find the correct option:

(a) 6.022×10236.022×1023 molecules of oxygen - Correct. Oxygen gas (O2O2) consists of oxygen molecules, and one mole of oxygen gas contains 6.022×10236.022×1023 oxygen molecules.

(b) 6.022×10236.022×1023 atoms of oxygen - Incorrect. Oxygen gas consists of molecules (O2O2), not individual atoms.

(c) 16 g16g of oxygen - Incorrect. This is the molar mass of oxygen, not the number of entities in one mole.

(d) 32 g32g of oxygen - Incorrect. This is the molar mass of O2O2, not the number of entities in one mole.

So, the correct answer is:

(a) 6.022×10236.022×1023 molecules of oxygen