Question

1. practice: chemical reactions are generally classified into five groups, defined below. balance each equation, using the gizmo for help. write out the balanced chemical equation on the lines. combination (or synthesis) - two or more elements combine to form a compound. na + o₂ → na₂o 4na + o2 = 2na2o n₂o₅ + h₂o → hno₃ n2o5+h2o=2hno3 decomposition - a compound breaks down into elements and/or simpler compounds. kno₃ → kno₂ + o₂ 2kno3=2kno2+o2 nan₃ → na + n₂ 2nan3 = 2na+ 3n2 combustion - a fuel reacts with oxygen to release carbon dioxide, water, and heat. ch₄ + o₂ → co₂ + h₂o c₂h₆ + o₂ → co₂ + h₂o single replacement - an element replaces another element in a compound. kcl + f₂ → kf + cl₂ mg + hcl → mgcl₂ + h₂ double replacement - two c another. agno₃ + k₂so₄ → ag

Explanation:

Step1: Balance $CH_4 + O_2

ightarrow CO_2 + H_2O$
Count atoms. On left: 1 C, 4 H, 2 O. On right: 1 C, 2 H, 3 O. Multiply $H_2O$ by 2 to balance H. Then multiply $O_2$ by 2 to balance O. So the balanced equation is $CH_4 + 2O_2
ightarrow CO_2+2H_2O$.

Step2: Balance $C_2H_6 + O_2

ightarrow CO_2 + H_2O$
Count atoms. Left: 2 C, 6 H, 2 O. Right: 1 C, 2 H, 3 O. First, multiply $CO_2$ by 2 to balance C and $H_2O$ by 3 to balance H. Then we have 7 O on right - hand side. Multiply $O_2$ by $\frac{7}{2}$, but we need whole - number coefficients, so multiply all coefficients by 2. The balanced equation is $2C_2H_6 + 7O_2
ightarrow 4CO_2+6H_2O$.

Step3: Balance $KCl + F_2

ightarrow KF+Cl_2$
Count atoms. Left: 1 K, 1 Cl, 2 F. Right: 1 K, 1 F, 2 Cl. Multiply KCl by 2 and KF by 2 to balance Cl and F. The balanced equation is $2KCl + F_2
ightarrow 2KF + Cl_2$.

Step4: Balance $Mg + HCl

ightarrow MgCl_2 + H_2$
Count atoms. Left: 1 Mg, 1 H, 1 Cl. Right: 1 Mg, 2 H, 2 Cl. Multiply HCl by 2 to balance Cl and H. The balanced equation is $Mg + 2HCl
ightarrow MgCl_2 + H_2$.

Step5: Balance $AgNO_3+K_2SO_4

ightarrow Ag_2SO_4 + KNO_3$
Count atoms. Left: 1 Ag, 1 N, 3 O, 2 K, 1 S. Right: 2 Ag, 1 N, 4 O, 1 K, 1 S. Multiply $AgNO_3$ by 2 and $KNO_3$ by 2 to balance Ag, N, K and O. The balanced equation is $2AgNO_3+K_2SO_4
ightarrow Ag_2SO_4 + 2KNO_3$.

Answer:

$CH_4 + 2O_2
ightarrow CO_2+2H_2O$
$2C_2H_6 + 7O_2
ightarrow 4CO_2+6H_2O$
$2KCl + F_2
ightarrow 2KF + Cl_2$
$Mg + 2HCl
ightarrow MgCl_2 + H_2$
$2AgNO_3+K_2SO_4
ightarrow Ag_2SO_4 + 2KNO_3$