Question

2naoh(aq) + znbr₂(aq) → 2nabr(aq) + zn(oh)₂(s)
element | number of atoms
na |
o |
h |
zn |
br |

Explanation:

Step1: Calculate Na atoms

In \(2\text{NaOH}\), Na has a coefficient of 2, and in \(2\text{NaBr}\), Na also has a coefficient of 2. So total Na atoms: \(2 + 2 = 4\)? Wait, no, wait. Wait, the reaction is \(2\text{NaOH}(aq) + \text{ZnBr}_2(aq) ightarrow 2\text{NaBr}(aq) + \text{Zn(OH)}_2(s)\). Let's count each element:

For Na: In \(2\text{NaOH}\), there are 2 Na atoms. In \(2\text{NaBr}\), there are 2 Na atoms. Wait, no, wait, the coefficients: \(2\text{NaOH}\) means 2 moles of NaOH, so Na: 2*1 = 2. \(2\text{NaBr}\) means 2 moles of NaBr, so Na: 2*1 = 2. Wait, no, that can't be. Wait, no, the left side: \(2\text{NaOH}\) has 2 Na, \(\text{ZnBr}_2\) has 0 Na. Right side: \(2\text{NaBr}\) has 2 Na, \(\text{Zn(OH)}_2\) has 0 Na. Wait, that's a mistake. Wait, no, the reaction is balanced? Let's check again.

Wait, the reaction: \(2\text{NaOH} + \text{ZnBr}_2 ightarrow 2\text{NaBr} + \text{Zn(OH)}_2\). Let's count each element:

Na: Left: 2 (from 2NaOH). Right: 2 (from 2NaBr). Correct.

O: Left: 2 (from 2NaOH, each NaOH has 1 O, so 2*1=2). Right: 2 (from Zn(OH)₂, which has 2 O). Correct.

H: Left: 2 (from 2NaOH, each has 1 H, so 2*1=2). Right: 2 (from Zn(OH)₂, 2 H). Correct.

Zn: Left: 1 (from ZnBr₂). Right: 1 (from Zn(OH)₂). Correct.

Br: Left: 2 (from ZnBr₂). Right: 2 (from 2NaBr, each NaBr has 1 Br, so 2*1=2). Correct. Oh! I see, I messed up earlier. So for each element:

Na: Left: 2 (from 2NaOH) + 0 (from ZnBr₂) = 2. Right: 2 (from 2NaBr) + 0 (from Zn(OH)₂) = 2. Wait, but the problem is to count the total number of atoms in the reaction (left + right)? No, wait, the table is probably asking for the total number of atoms in the entire reaction (both sides) or per side? Wait, the problem is to fill in the number of atoms for each element in the reaction. Wait, maybe it's the total number of atoms in the reaction (sum of left and right? No, that doesn't make sense. Wait, no, the reaction is a chemical equation, so we need to count the number of atoms of each element in the entire equation (both reactants and products) to check conservation.

Wait, let's do it properly:

Element Na:

Reactants: \(2\text{NaOH}\) has 2 Na atoms (2*1), \(\text{ZnBr}_2\) has 0. So total Na in reactants: 2.

Products: \(2\text{NaBr}\) has 2 Na atoms (2*1), \(\text{Zn(OH)}_2\) has 0. So total Na in products: 2. Wait, but that's 2 + 2? No, no, the table is probably asking for the total number of atoms in the reaction (sum of all atoms, reactants and products)? No, that doesn't make sense. Wait, maybe the table is for the entire reaction (all species), so we need to count each atom:

Let's list all species:

Reactants: \(2\text{NaOH}\) (aq), \(\text{ZnBr}_2\) (aq)

Products: \(2\text{NaBr}\) (aq), \(\text{Zn(OH)}_2\) (s)

Now, expand each:

\(2\text{NaOH}\) = 2 Na⁺ + 2 OH⁻

\(\text{ZnBr}_2\) = Zn²⁺ + 2 Br⁻

\(2\text{NaBr}\) = 2 Na⁺ + 2 Br⁻

\(\text{Zn(OH)}_2\) = Zn²⁺ + 2 OH⁻

Now count each element:

Na: 2 (from 2NaOH) + 2 (from 2NaBr) = 4? Wait, no, that's not right. Wait, no, in the reaction, the atoms are conserved, so the total number of Na atoms should be the same on both sides. Wait, the left side has 2 Na (from 2NaOH) and the right side has 2 Na (from 2NaBr). But if we count all atoms (reactants and products), that's double? No, that's a mistake. Wait, no, the reaction is a chemical equation, so we count the number of atoms of each element in the entire equation (i.e., sum of reactants and products? No, that's not how it works. The correct way is to count the number of atoms of each element in the reactants (left side) and products (right side), but since it's a balanced equation, they should be equal. Wait, the table says "Number of atoms" – maybe it's the total number of atoms of each element in the entire reaction (i.e., sum of all atoms, reactants and products)? But that would be double, because reactants and products are separate. Wait, no, the problem is probably asking for the number of atoms of each element in the balanced equation, i.e., the total number of atoms of each element in the entire reaction (reactants + products)? No, that doesn't make sense. Wait, let's look at the reaction again:

Reactants: \(2\text{NaOH}\) and \(\text{ZnBr}_2\)

Products: \(2\text{NaBr}\) and \(\text{Zn(OH)}_2\)

Let's count each element in all species:

Na:

- \(2\text{NaOH}\): 2 Na atoms

- \(\text{ZnBr}_2\): 0 Na atoms

- \(2\text{NaBr}\): 2 Na atoms

- \(\text{Zn(OH)}_2\): 0 Na atoms

Total Na atoms: 2 + 0 + 2 + 0 = 4? Wait, that can't be. Wait, no, the reaction is a chemical change, but the number of atoms is conserved. So the total number of Na atoms in reactants is 2 (from 2NaOH), and in products is 2 (from 2NaBr). So total Na atoms in the system (reactants + products) is 2 + 2 = 4? But that's not how we usually count. Wait, maybe the problem is asking for the number of atoms of each element in the entire equation (i.e., the sum of all atoms, regardless of reactants or products). Let's do that:

Na:

- 2NaOH: 2 Na

- ZnBr₂: 0 Na

- 2NaBr: 2 Na

- Zn(OH)₂: 0 Na

Total: 2 + 0 + 2 + 0 = 4

O:

- 2NaOH: 2 O (each NaOH has 1 O, 2*1=2)

- ZnBr₂: 0 O

- 2NaBr: 0 O

- Zn(OH)₂: 2 O (each Zn(OH)₂ has 2 O)

Total: 2 + 0 + 0 + 2 = 4

H:

- 2NaOH: 2 H (each NaOH has 1 H, 2*1=2)

- ZnBr₂: 0 H

- 2NaBr: 0 H

- Zn(OH)₂: 2 H (each Zn(OH)₂ has 2 H)

Total: 2 + 0 + 0 + 2 = 4

Zn:

- 2NaOH: 0 Zn

- ZnBr₂: 1 Zn

- 2NaBr: 0 Zn

- Zn(OH)₂: 1 Zn

Total: 0 + 1 + 0 + 1 = 2

Br:

- 2NaOH: 0 Br

- ZnBr₂: 2 Br

- 2NaBr: 2 Br

- Zn(OH)₂: 0 Br

Total: 0 + 2 + 2 + 0 = 4

Wait, but that seems odd. Alternatively, maybe the problem is asking for the number of atoms of each element in the reactants (left side) or products (right side), but since it's balanced, they should be equal. Wait, the reaction is balanced, so for each element, the number of atoms on the left (reactants) is equal to the number on the right (products). Let's check:

Na: Left: 2 (from 2NaOH) + 0 (from ZnBr₂) = 2. Right: 2 (from 2NaBr) + 0 (from Zn(OH)₂) = 2.

O: Left: 2 (from 2NaOH) + 0 (from ZnBr₂) = 2. Right: 0 (from 2NaBr) + 2 (from Zn(OH)₂) = 2.

H: Left: 2 (from 2NaOH) + 0 (from ZnBr₂) = 2. Right: 0 (from 2NaBr) + 2 (from Zn(OH)₂) = 2.

Zn: Left: 0 (from 2NaOH) + 1 (from ZnBr₂) = 1. Right: 0 (from 2NaBr) + 1 (from Zn(OH)₂) = 1.

Br: Left: 0 (from 2NaOH) + 2 (from ZnBr₂) = 2. Right: 2 (from 2NaBr) + 0 (from Zn(OH)₂) = 2.

Ah! So the number of atoms of each element in the reactants (left side) is:

Na: 2

O: 2

H: 2

Zn: 1

Br: 2

And in the products (right side) is the same. But the table says "Number of atoms" – maybe it's the total number of atoms of each element in the entire reaction (reactants + products)? But that would be 2 + 2 = 4 for Na, 2 + 2 = 4 for O, 2 + 2 = 4 for H, 1 + 1 = 2 for Zn, 2 + 2 = 4 for Br. But that seems like double. Wait, maybe the problem is asking for the number of atoms of each element in the balanced equation, i.e., the coefficient times the subscript. Let's re-express the equation with all atoms:

Reactants:

- 2NaOH: 2 Na, 2 O, 2 H

- ZnBr₂: 0 Na, 0 O, 0 H, 1 Zn, 2 Br

Products:

- 2NaBr: 2 Na, 0 O, 0 H, 0 Zn, 2 Br

- Zn(OH)₂: 0 Na, 2 O, 2 H, 1 Zn, 0 Br

Now, sum all atoms:

Na: 2 (reactants) + 2 (products) = 4

O: 2 (reactants) + 2 (products) = 4

H: 2 (reactants) + 2 (products) = 4

Zn: 1 (reactants) + 1 (products) = 2

Br: 2 (reactants) + 2 (products) = 4

But that seems like the total number of atoms of each element in the entire reaction (both sides). Maybe that's what the table is asking for. Let's confirm:

For Na:

In 2NaOH: 2 Na atoms.

In ZnBr₂: 0 Na atoms.

In 2NaBr: 2 Na atoms.

In Zn(OH)₂: 0 Na atoms.

Total: 2 + 0 + 2 + 0 = 4.

O:

2NaOH: 2 O.

ZnBr₂: 0 O.

2NaBr: 0 O.

Zn(OH)₂: 2 O.

Total: 2 + 0 + 0 + 2 = 4.

H:

2NaOH: 2 H.

ZnBr₂: 0 H.

2NaBr: 0 H.

Zn(OH)₂: 2 H.

Total: 2 + 0 + 0 + 2 = 4.

Zn:

2NaOH: 0 Zn.

ZnBr₂: 1 Zn.

2NaBr: 0 Zn.

Zn(OH)₂: 1 Zn.

Total: 0 + 1 + 0 + 1 = 2.

Br:

2NaOH: 0 Br.

ZnBr₂: 2 Br.

2NaBr: 2 Br.

Zn(OH)₂: 0 Br.

Total: 0 + 2 + 2 + 0 = 4.

Yes, that makes sense. So the number of atoms for each element is:

Na: 4

O: 4

H: 4

Zn: 2

Br: 4

Wait, but let's check again. Wait, the reaction is \(2\text{NaOH} + \text{ZnBr}_2 ightarrow 2\text{NaBr} + \text{Zn(OH)}_2\). Let's count the number of atoms of each element in the entire equation (i.e., all molecules):

- Na: 2 (from 2NaOH) + 2 (from 2NaBr) = 4

- O: 2 (from 2NaOH) + 2 (from Zn(OH)₂) = 4

- H: 2 (from 2NaOH) + 2 (from Zn(OH)₂) = 4

- Zn: 1 (from ZnBr₂) + 1 (from Zn(OH)₂) = 2

- Br: 2 (from ZnBr₂) + 2 (from 2NaBr) = 4

Yes, that's correct. So the table should be filled with:

Na: 4

O: 4

H: 4

Zn: 2

Br: 4

Wait, but let's verify with the balanced equation. The balanced equation has equal numbers of each element on both sides, so the total number of atoms (reactants + products) is twice the number on one side. For example, Na: 2 on left, 2 on right, total 4. O: 2 on left, 2 on right, total 4. Etc. So that's the case.

Step2: Count O atoms

Left side: 2NaOH has 2 O atoms (2*1). Right side: Zn(OH)₂ has 2 O atoms (2). Total O atoms: 2 + 2 = 4.

Step3: Count H atoms

Left side: 2NaOH has 2 H atoms (2*1). Right side: Zn(OH)₂ has 2 H atoms (2). Total H atoms: 2 + 2 = 4.

Step4: Count Zn atoms

Left side: ZnBr₂ has 1 Zn atom. Right side: Zn(OH)₂ has 1 Zn atom. Total Zn atoms: 1 + 1 = 2.

Step5: Count Br atoms

Left side: ZnBr₂ has 2 Br atoms. Right side: 2NaBr has 2 Br atoms (2*1). Total Br atoms: 2 + 2 = 4.

Answer:

Na: 4
O: 4
H: 4
Zn: 2
Br: 4

(Note: If the table is asking for the number of atoms in the reactants or products, the numbers would be 2, 2, 2, 1, 2 respectively, but based on the problem's table and the need to count all atoms in the reaction, the total is as above.)