Question #98201

1. Calculate the percent composition by mass of nitric acid.

2. What is the percent composition of chromium in K2Cr2O7?

3. Find the following:

Given: Sodium Dihydrogen Phosphate, NaH2PO4

a.) formula weight

b.) percent composition of oxygen

c.) weight in grams of 2.7 moles

2. What is the percent composition of chromium in K2Cr2O7?

3. Find the following:

Given: Sodium Dihydrogen Phosphate, NaH2PO4

a.) formula weight

b.) percent composition of oxygen

c.) weight in grams of 2.7 moles

Expert's answer

**Solution.**

"w(E) = \\frac{Ar \\times n \\times 100}{M}"

1.

"w(H) = \\frac{1*1*100}{63} = 1.59 \\%"

"w(N) = \\frac{14*1*100}{63} = 22.22 \\%"

"w(O) = 100.00 \\% - 22.22 \\% - 1.59 \\% = 76.19 \\%"

2.

"w(Cr) = \\frac{2 \\times 52 \\times 100}{294} = 35.37 \\%"

3.

a)

"M(NaH2PO4) = 23 + (2 \\times 1) + 31 + (4 \\times 16) = 120 \\ g\/mol"

b)

"w(O) = \\frac{4 \\times 16 \\times 100}{120} = 53.33 \\%"

c)

"n = \\frac{m}{M}"

"m = n \\times M"

"m = 2.7 \\times 120 = 324.0 \\ g"

**Answer:**

1.

w(H) = 1.59 %

w(N) = 22.22 %

w(O) = 76.19 %

2.

w(Cr) = 35.37 %

3.

a)

M(NaH2PO4) = 120 g/mol

b)

w(O) = 53.33 %

c)

m (NaH2PO4) = 324 g

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