Answer:
Cu + 4 HNO₃ → Cu(NO₃)₂ + 2 NO₂ + 2 H₂O
Explanation:
Step 1: Write down the chemical formulas of given substances,
Copper Metal = Cu
Nitric Acid = HNO₃
Copper (II) Nitrate = Cu(NO₃)₂
Nitrogen Dioxide = NO₂
Water = H₂O
Step 2: Write down the unbalance Chemical equation,
Cu + HNO₃ → Cu(NO₃)₂ + NO₂ + H₂O
Step 3: Balance Cu atoms on both sides;
The number of Cu atoms on both sides are same. Hence, there number will remain the same.
Step 4: Balance N atoms on both sides;
As there is 1 N atom on left hand side and 3 N atoms on right hand side, so we will multiply HNO₃ by 3 to balance N on both sides, hence,
Cu + 3 HNO₃ → Cu(NO₃)₂ + NO₂ + H₂O
Step 5: Balance O atoms on both sides;
As there are 9 O atom on left hand side and 9 O atoms on right hand side, so they are balance.
Step 6: Balance H atoms on both sides;
As there are 3 H atom on left hand side and 2 H atoms on right hand side, so we will multiply H₂O by 2 as,
Cu + 3 HNO₃ → Cu(NO₃)₂ + NO₂ + 2 H₂O
By doing so the number of O atoms got imbalanced, so to balance O atoms again we will multiply HNO₃ by 4 as,
Cu + 4 HNO₃ → Cu(NO₃)₂ + NO₂ + 2 H₂O
Now, The Cu and H atoms are balanced, and the O atoms are greater on left hand side and the N atoms are greater on right hand side, therefore we will multiply NO₂ by 2 to balance both N and O as,
Cu + 4 HNO₃ → Cu(NO₃)₂ + 2 NO₂ + 2 H₂O
= 0.001 
. Therefore 200 
. Hope this helps.