Question

five numericals of molarity​

Answer 1

Explanation:

Problem #1: Sea water contains roughly 28.0 g of NaCl per liter. What is the molarity of sodium chloride in sea water?

Solution:

MV = grams / molar mass

(x) (1.00 L) = 28.0 g / 58.443 g mol¯1

x = 0.4790993 M

to three significant figures, 0.479 M

Problem #2: What is the molarity of 245.0 g of H2SO4 dissolved in 1.000 L of solution?

Solution:

MV = grams / molar mass

(x) (1.000 L) = 245.0 g / 98.0768 g mol¯1

x = 2.49804235 M

to four sig figs, 2.498 M

If the volume had been specified as 1.00 L (as it often is in problems like this), the answer would have been 2.50 M, NOT 2.5 M. You want three sig figs in the answer and 2.5 is only two SF.

Problem #3: What is the molarity of 5.30 g of Na2CO3 dissolved in 400.0 mL solution?

Solution:

MV = grams / molar mass

(x) (0.4000 L) = 5.30 g / 105.988 g mol¯1

0.12501415 M

x = 0.125 M (to three sig figs)

Problem #4: What is the molarity of 5.00 g of NaOH in 750.0 mL of solution?

Solution:

MV = grams / molar mass

(x) (0.7500 L) = 5.00 g / 39.9969 g mol¯1

(x) (0.7500 L) = 0.1250097 mol <--- threw in an extra step

x = 0.1666796 M

x = 0.167 M (to three SF)

Problem #5: How many moles of Na2CO3 are there in 10.0 L of 2.00 M solution?

Solution:

M = moles of solute / liters of solution

2.00 M = x / 10.0 L

x = 20.0 mol

Suppose the molarity was listed as 2.0 M (two sig figs). How to display the answer? Like this:

20. mol