Hoang's Unit 4 Test Review 2

• 54 g

• 36 g

• 18 g

• 72 g

Answer explanation

To convert moles to grams, multiply the number of moles by the molar mass. Here, 3 moles of H2O x 18 g/mol = 54 g. Thus, the correct answer is 54 g.

Tags

NGSS.HS-PS1-7

• 1 mole

• 2 moles

• 3 moles

• 4 moles

Answer explanation

To find the number of moles, use the formula: moles = mass (g) / molar mass (g/mol). Here, moles = 88 g / 44 g/mol = 2 moles. Therefore, the correct answer is 2 moles.

Tags

NGSS.HS-PS1-7

Answer explanation

To find the number of molecules in 2 moles of nitrogen gas (N2), multiply the number of moles by Avogadro's number: 2 moles × 6.022 × 10^23 molecules/mol = 1.204 × 10^24 molecules. Thus, the correct answer is 1.204 × 10^24 molecules.

• 88.89%

• 44.44%

• 33.33%

• 11.11%

Answer explanation

To find the percent composition of oxygen in H2O, divide the molar mass of oxygen (16 g/mol) by the molar mass of water (18 g/mol) and multiply by 100. (16/18) * 100 = 88.89%. Thus, the correct answer is 88.89%.

• 90 g

• 45 g

• 180 g

• 60 g

Answer explanation

To find the mass of glucose, multiply the number of moles by the molar mass: 0.5 moles × 180 g/mol = 90 g. Therefore, the correct answer is 90 g.

• 1 mole

• 2 moles

• 3 moles

• 4 moles

Answer explanation

To find moles of NaCl, use the formula: moles = mass (g) / molar mass (g/mol). Here, moles = 117 g / 58.5 g/mol = 2 moles. Thus, the correct answer is 2 moles.

Tags

NGSS.HS-PS1-7

Calculate the number of particles in 0.25 moles of helium gas using Avogadro's number.

Answer explanation

To find the number of particles in 0.25 moles of helium, multiply by Avogadro's number (6.022 x 10^23). Thus, 0.25 moles x 6.022 x 10^23 = 1.5055 x 10^23 particles, making the correct choice 1.5055 x 10^23 particles.

• 75%

• 25%

• 50%

• 60%

Answer explanation

To find the percent composition of carbon in methane (CH₄), divide the mass of carbon (12 g/mol) by the molar mass of methane (16 g/mol) and multiply by 100. (12/16) x 100 = 75%. Thus, the correct answer is 75%.

• 0.5 moles

• 1 mole

• 2 moles

• 3 moles

Answer explanation

To convert molecules to moles, use Avogadro's number (6.022 x 10^{23} molecules/mole). Divide 3.01 x 10^{23} by 6.022 x 10^{23} to get approximately 0.5 moles. Thus, the correct answer is 0.5 moles.

• 441 g

• 392 g

• 445 g

• 490 g

Answer explanation

To find the weight of 4.5 moles of H2SO4, multiply the number of moles by the molar mass: 4.5 moles × 98 g/mol = 441 g. Thus, the sample weighs 441 g.