When $81.0 \ g$ of aluminium is allowed to react with $128.0 \ g$ of oxygen gas,the mass of aluminium oxide produced in grams is $..........$ $(Nearest \ integer)$. Given: Molar mass of $Al$ is $27.0 \ g \ mol^{-1}$,Molar mass of $O$ is $16.0 \ g \ mol^{-1}$.

The amount of $BaSO_4$ formed upon mixing $100 \ mL$ of $20.8 \%$ $BaCl_2$ solution with $50 \ mL$ of $9.8 \%$ $H_2SO_4$ solution will be ............. $g$
( $Ba = 137, Cl = 35.5, S = 32, H = 1$ and $O = 16$ )

Butane reacts with oxygen to produce carbon dioxide and water following the equation given below: $C_4H_{10(g)} + \frac{13}{2} O_{2(g)} \rightarrow 4 CO_{2(g)} + 5 H_2O_{(l)}$. If $174.0 \ kg$ of butane is mixed with $320.0 \ kg$ of $O_2$,the volume of water formed in litres is $...........$ (Nearest integer). [$Given$: $(a)$ Molar mass of $C, H, O$ are $12, 1, 16 \ g \ mol^{-1}$ respectively,$(b)$ Density of water $= 1 \ g \ mL^{-1}$]

The amount of heat evolved when $500 \text{ cm}^{3}$ of $0.1 \text{ M } HCl$ is mixed with $200 \text{ cm}^{3}$ of $0.2 \text{ M } NaOH$ is (in $\text{ kJ}$)

When $400 \ mL$ of $0.2 \ M \ H_2SO_4$ solution is mixed with $600 \ mL$ of $0.1 \ M \ NaOH$ solution,the increase in temperature of the final solution is $...... \times 10^{-2} \ K$. (Round off to the Nearest Integer).
$\left[ \text{Use } : H^{+}_{(aq)} + OH^{-}_{(aq)} \rightarrow H_2O : \Delta_{r}H = -57.1 \ kJ \ mol^{-1} \right]$
Specific heat of $H_2O = 4.18 \ J \ K^{-1} \ g^{-1}$
Density of $H_2O = 1.0 \ g \ cm^{-3}$
Assume no change in volume of solution on mixing.

When copper is reacted with a certain concentration of nitric acid,nitric oxide and nitrogen dioxide are produced in equal volumes according to the following reaction:
$xCu + yHNO_3 \to xCu(NO_3)_2 + NO + NO_2 + 3H_2O$
What are the stoichiometric coefficients $x$ and $y$?