Question

should do: law of conservation of mass practice pg. 13

1. ____n₂ + 47g 3h₂ → 63g nh₃
2. 78g kclo₃ → ____2kcl + 36g 3o₂
3. 152g nacl + 36g f₂ → 127g 2naf + ____cl₂
4. ____h₂ + 12g o₂ → 33g h₂o
5. 57g pb(oh)₂ + 46g 2hcl → ____2h₂o + 102gpbcl₂
6. 26g 2albr₃ + ____3k₂so₄ → 14g 6kbr + 38g al₂(so₄)₃
7. 67g ch₄ + 57g 2o₂ → 13g co₂ + ____2h₂o
8. 77g c₃h₈ + ____5o₂ → 98g 3co₂ +16g 4h₂o
9. ____2c₈h₁₈ + 63g 25o₂ → 14g 16co₂ + 82g 18h₂o

10.____fecl₃ + 363g 3naoh → 112g fe(oh)₃ + 408g 3nacl

1. 512g 4p + 124g 5o₂ → ____2p₂o₅
2. 401g 2na + ____2h₂o → 536g 2naoh + 281g h₂

Explanation:

Step1: Apply Law of Conservation of Mass

The total mass of reactants equals total mass of products. For each problem, solve for the unknown mass $m$:
$m_{\text{unknown}} = \sum m_{\text{products}} - \sum m_{\text{known reactants}}$
or
$m_{\text{unknown}} = \sum m_{\text{reactants}} - \sum m_{\text{known products}}$

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Problem 1

Step1: Calculate unknown $N_2$ mass

$m_{\text{N}_2} = 63\ \text{g} - 47\ \text{g} = 16\ \text{g}$

Problem 2

Step1: Calculate unknown $2\text{KCl}$ mass

$m_{\text{2KCl}} = 78\ \text{g} - 36\ \text{g} = 42\ \text{g}$

Problem 3

Step1: Calculate unknown $\text{Cl}_2$ mass

$m_{\text{Cl}_2} = (152\ \text{g} + 36\ \text{g}) - 127\ \text{g} = 61\ \text{g}$

Problem 4

Step1: Calculate unknown $\text{H}_2$ mass

$m_{\text{H}_2} = 33\ \text{g} - 12\ \text{g} = 21\ \text{g}$

Problem 5

Step1: Calculate unknown $2\text{H}_2\text{O}$ mass

$m_{\text{2H}_2\text{O}} = (57\ \text{g} + 46\ \text{g}) - 102\ \text{g} = 1\ \text{g}$

Problem 6

Step1: Calculate unknown $3\text{K}_2\text{SO}_4$ mass

$m_{\text{3K}_2\text{SO}_4} = (14\ \text{g} + 38\ \text{g}) - 26\ \text{g} = 26\ \text{g}$

Problem 7

Step1: Calculate unknown $2\text{H}_2\text{O}$ mass

$m_{\text{2H}_2\text{O}} = (67\ \text{g} + 57\ \text{g}) - 13\ \text{g} = 111\ \text{g}$

Problem 8

Step1: Calculate unknown $5\text{O}_2$ mass

$m_{\text{5O}_2} = (98\ \text{g} + 16\ \text{g}) - 77\ \text{g} = 37\ \text{g}$

Problem 9

Step1: Calculate unknown $2\text{C}_8\text{H}_{18}$ mass

$m_{\text{2C}_8\text{H}_{18}} = (14\ \text{g} + 82\ \text{g}) - 63\ \text{g} = 33\ \text{g}$

Problem 10

Step1: Calculate unknown $\text{FeCl}_3$ mass

$m_{\text{FeCl}_3} = (112\ \text{g} + 408\ \text{g}) - 363\ \text{g} = 157\ \text{g}$

Problem 11

Step1: Calculate unknown $2\text{P}_2\text{O}_5$ mass

$m_{\text{2P}_2\text{O}_5} = 512\ \text{g} + 124\ \text{g} = 636\ \text{g}$

Problem 12

Step1: Calculate unknown $2\text{H}_2\text{O}$ mass

$m_{\text{2H}_2\text{O}} = (536\ \text{g} + 281\ \text{g}) - 401\ \text{g} = 416\ \text{g}$

Answer:

1. $\boldsymbol{16\ \text{g}}$
2. $\boldsymbol{42\ \text{g}}$
3. $\boldsymbol{61\ \text{g}}$
4. $\boldsymbol{21\ \text{g}}$
5. $\boldsymbol{1\ \text{g}}$
6. $\boldsymbol{26\ \text{g}}$
7. $\boldsymbol{111\ \text{g}}$
8. $\boldsymbol{37\ \text{g}}$
9. $\boldsymbol{33\ \text{g}}$
10. $\boldsymbol{157\ \text{g}}$
11. $\boldsymbol{636\ \text{g}}$
12. $\boldsymbol{416\ \text{g}}$