Given the following reaction, Cr(OH)3 + NaOH = NaCrO2 + 2H2O , how many grams of NaCrO2 can be produced from 83.3 g of Cr(OH)3?

Answer 1

To the best of my knowledge, the reaction of chromium hydroxide, Cr(OH)₃ with sodium hydroxide, NaOH, does not produce sodium chromite, NaCrO₂, but rather produces the complex anion called tetrahydroxochromate(III) which is Cr(OH)₄.

Cr(OH)₃(s) + OH-(aq) <==> Cr(OH₄)^-(aq)

Answer 2

Normally,

Chromium(III) hydroxide react with sodium hydroxide to produce sodium hexahydroxochromate(III). Sodium hydroxide - concentrated solution. 

But for calculation purpose if the reaction given in problem is what it is. Please read answers to your questions below.

Cr(OH)3+ NaOH-->NaCrO2 +2H2O

1 mole of Cr(OH)3 + 1 mole of NaOH will produce 1 mole of NaCrO2

Here we first need to find molar mass of Cr(OH)3 and NaCrO2

Molar mass of Cr(OH)3

Cr+3 (O)+ 3*(H)

=51.996+3*(15.999)+3(1.008) =103.017 ≅ 103

Molar Mass of NaCrO2

Na+Cr+2*(O)

=22.990+51.996+2*(15.999) = 106.984 ≅107

Mole of Cr(OH)3

Mole = weight in gram / Molar mass

=83.3 g of Cr(OH)3/ 103 ( molar mass of Cr(OH)3)

=.8087 mole of Cr(OH)3

Back to equation

Cr(OH)3+ NaOH-->NaCrO2 +2H2O

mole of Cr(OH)3 = mole of NaCrO2

.8087 mole of Cr(OH)3 =.8087 mole of NaCrO2

we need answers in Gram thus, we will need to multiply mole by molar mass to get the gram NaCrO2

.8087 mol of NaCrO2 * 107gram/mol = 86.53 grams of NaCrO2

Checking significant number is very important when calculating any chemistry problems

Initially the weight given in three significant number, thus our answer should be in three significant number.

That leave us with final answer 86.5g of NaCrO2 will be produce from 83.3g of Cr(OH)3.