What mass is needed to prepare 50.0 mL of 1.00 M solution? What is the molarity

Question

What mass is needed to prepare 50.0 mL of 1.00 M solution? What is the molarity of a solution prepared by dissolving 3.4g of NH_3 in 500 mL of solution? What is the molarity of a 0.50 mole of CaCl_2 is dissolved up to L of solution? What is the density of a sample of O_2 gas if it exerts a pressure of 1.38 atm at 300 K? How many moles are present in a 2.00 L sample of gas at 30 degree C and 0.821 atm? What is the molar mass of a gas if 10 g occupy 8.2 L at 380 torr and 27 degree c? A compound with the empirical formula CH_2O has a molar mass of 90 g/mol. The molecular formula is:

Explanation / Answer

Question 14

I2 molecular weight = 253.809 g/mol

mass of the I2 to prepare 50 ml of 1M solution = 253.809 g/mol x 0.05 Mol = 12.69 gm

Question 15

Molarity of the solution = 3.4 x 1000 / 500 x 17 = 0.4 M

Question 16

0.5 Mole of CaCl2 (Molar mass: 110.98 g/mol) = 0.5 x 110.98 = 55.49 g

Molarity of the solution = 55.49 / 110.98 x 2 = 0.25 M

Question 18

PV = nRT

where:

P is the pressure of the gas = 0.821 atm

V is the volume of the gas = 2 Lit

n is the amount of substance of gas (in moles) = ?

R is gas constant = = 0.0821 L atm K-1 Mol-1

T is the absolute temperature of the gas= 273 +30 = 303 K

substitute in the equation and calculate n in moles

n = 0.821 x 2 / 303 x 0.0821 = 0.066 Moles

Question 19

Use the above equatio to find Moles of the gas

380 torr = 0.5 atm

n = 0.5 x 8.2 /300 x 0.0821 = 0.166 Moles

Molecular weight = 10 gm /0.166 Mole = 60.07 g /mole

Quesiton 20

Molecular weight of CH2O = 30

Molar mass of the compound = 90 g/mole

Hence 3 units of CH2O is present. Hence molecular formula = C3H6O3

.

V1 =

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