1. In the photographic developing process, silver bromide is dissolved by adding

ID: 1006617 • Letter: 1

Question

In the photographic developing process, silver bromide is dissolved by adding sodium thiosulfate.

AgBr(s) + 2 Na2S2O3(aq) Na3Ag(S2O3)2(aq) + NaBr(aq)

If you want to dissolve 0.194 g of AgBr, what volume of 0.0138 M Na2S2O3, in milliliters, should be used?

_____mL

What volume of 0.226 M NaOH, in milliliters, contains 25.0 g of NaOH ?

Volume = ______mL

The reaction of methane and water is one way to prepare hydrogen for use as a fuel:

CH4(g) + H2O(g) CO(g) + 3 H2(g)

What mass of the excess reactant remains when the reaction is completed if the limiting reactant is H2O?

_______ g of the excess reactant

(1) AgBr(s) + 2 Na2S2O3(aq) Na3Ag(S2O3)2(aq) + NaBr(aq)

Molar mass of AgBr is 188 g/mol

Given mass of AgBr = 0.194 g

Number of moles , n = mass/molar mass

= 0.194 / 188

= 0.001 moles

According to the balanced reaction ,

1 mole of AgBr reacts with 2 moles of Na2S2O3

0.001 mole of AgBr reacts with M moles of Na2S2O3

M = ( 0.001x2) / 1

= 0.002 moles

So Volume of Na2S2O3 is , V = number of moles / molarity

= 0.002 mol / 0.0138

= 0.149 L

= 149 mL

(2) What volume of 0.226 M NaOH, in milliliters, contains 25.0 g of NaOH ?

We know that Molarity , M = ( mass/Molar mass) x ( 1000/Volume in mL)

0.226 = ( 25.0/40) x ( 1000 / Volume in L)

So Volume of the solution , V = 2765 mL

(3) This reaction is incomplete.It involves the masses of the reactants.

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